Vietnam's Transport Minister Dinh La Thang (L) walks with Prime Minister Nguyen Tan Dung (C) at a ceremony in Hanoi, Vietnam July 2, 2015. Picture taken July 2, 2015. REUTERS/Kham/Files 

U.S. President Barack Obama and other leaders take part in a group photo at the10-nation Association of Southeast Asian Nations (ASEAN) summit at Sunnylands in Rancho Mirage, California, February 16, 2016. From left are Asean Secretary General Le Luong Minh, Sultan of Brunei Hassanal Bolkiah, Cambodia Prime Minister Hun Sen, Indonesian President Joko Widodo, Malaysia Prime Minister Najib Razak, Laos President Choummaly Sayasone, Obama, Philippine President Benigno Aquino, Singapore Prime Minister Lee Hsien Loong, Thailand Prime Minister Prayuth Chan-ocha , Vietnam Prime Minister Nguyen Tan Dung and Myanmar Vice President Nyan Tun. REUTERS/Kevin Lamarque

U.S. President Barack Obama and leaders from the 10-nation Association of Southeast Asian Nations (ASEAN) summit gather for a family photo in Rancho Mirage, California February 16, 2016. From left are Asean Secretary General Le Luong Minh, Sultan of Brunei Hassanal Bolkiah, Cambodia Prime Minister Hun Sen, Indonesian President Joko Widodo, Malaysia Prime Minister Najib Razak, Laos President Choummaly Sayasone, Obama, Philippine President Benigno Aquino, Singapore Prime Minister Lee Hsien Loong, Thailand Prime Minister Prayuth Chan-ocha , Vietnam Prime Minister Nguyen Tan Dung and Myanmar Vice President Nyan Tun. REUTERS/Mike Blake

U.S. President Barack Obama waves during a group photo at the 10-nation Association of Southeast Asian Nations (ASEAN) summit at Sunnylands in Rancho Mirage, California February 16, 2016. From left are Asean Secretary General Le Luong Minh, Sultan of Brunei Hassanal Bolkiah, Cambodia Prime Minister Hun Sen, Indonesian President Joko Widodo, Malaysia Prime Minister Najib Razak, Laos President Choummaly Sayasone, Obama, Philippine President Benigno Aquino, Singapore Prime Minister Lee Hsien Loong, Thailand Prime Minister Prayuth Chan-ocha , Vietnam Prime Minister Nguyen Tan Dung and Myanmar Vice President Nyan Tun. REUTERS/Kevin Lamarque

Nguyen Tan Dung, Prime Minister of Vietnam listens to U.S. President Barack Obama speak during a 10-nation Association of Southeast Asian Nations (ASEAN) summit in Rancho Mirage, California February 15, 2016. Obama will press leaders from Southeast Asia to boost trade and back a common stance on the South China Sea. REUTERS/Mike Blake

U.S. President Barack Obama (C) addresses leaders at a 10-nation Association of Southeast Asian Nations (ASEAN) summit in Rancho Mirage, California February 15, 2016. Obama is expected to press leaders from Southeast Asia to boost trade and back a common stance on the South China Sea. The leaders (L to R) Le Luong Minh, Secretary General of the Association of Southeast Asian Nations, Vietnam Prime Minister Nguyen Tan Dung, Thailand Prime Minister Prayuth Chan-ocha, Singapore Prime Minister Lee Hsien Loong, Philippine President Benigno Aquino, Laos President Choummaly Sayasone, U.S. President Barack Obama, Sultan of Brunei Hassanal Bolkiah, Cambodia Prime Minister Hun Sen, Indonesian President Joko Widodo, Malaysia Prime Minister Najib Razak and Myanmar Vice President U Nyan Tun. REUTERS/Mike Blake 

U.S. President Barack Obama (C) addresses leaders at a 10-nation Association of Southeast Asian Nations (ASEAN) summit in Rancho Mirage, California February 15, 2016. Obama is expected to press leaders from Southeast Asia to boost trade and back a common stance on the South China Sea. The leaders (L to R) Vietnam Prime Minister Nguyen Tan Dung, Thailand Prime Minister Prayuth Chan-ocha, Singapore Prime Minister Lee Hsien Loong, Philippine President Benigno Aquino, Laos President Choummaly Sayasone, U.S. President Barack Obama, Sultan of Brunei Hassanal Bolkiah, Cambodia Prime Minister Hun Sen, Indonesian President Joko Widodo, Malaysia Prime Minister Najib Razak and Myanmar Vice President U Nyan Tun. REUTERS/Mike Blake 

Top leaders of Vietnam's Communist Party attend the Closing Ceremony of the 12th National Congress of Vietnam Communist Party in Hanoi, Vietnam January 28, 2016. Front row are: General Secretary of Vietnam's Communist Party Nguyen Phu Trong (L) and Prime Minister Nguyen Tan Dung. Back row are: Ho Chi Minh City's Party Chief Le Thanh Hai (L), Hanoi City's Party Chief Pham Quang Nghi (C) and Defence Minister Phung Quang Thanh. REUTERS/Kham 

Vietnam's Prime Minister Nguyen Tan Dung arrives at the National Convention Center for the last day of the 12th National Congress of Vietnam's Communist Party (VCP), in Hanoi, Vietnam, January 28, 2016. REUTERS/Minh Hoang/Pool 

Leaders are seen after the voting session for the new Central Committee during the 12th National Congress of the ruling Vietnam Communist Party in Hanoi, Vietnam, January 26, 2016. (bottom L-R) Vietnam's President Truong Tan Sang, General Secretary of Communist Party Nguyen Phu Trong and Vietnam's Prime Minister Nguyen Tan Dung (top L-R) Vice Chairwoman of National Assembly Tong Thi Phong, Ho Chi Minh City's Party Chief Le Thanh Hai and Hanoi City's Party Chief Pham Quang Nghi. REUTERS/Kham

Vietnam's Prime Minister Nguyen Tan Dung (C) is seen with Hanoi City's Party Chief Pham Quang Nghi (top L) and Defence Minister Phung Quang Thanh (top R) after voting for the new Central Committee during the 12th National Congress of the ruling Vietnam Communist Party in Hanoi, Vietnam, January 26, 2016. REUTERS/Kham

Vietnam's Prime Minister Nguyen Tan Dung (L) walks away as Communist Party General Secretary Nguyen Phu Trong sits after voting for the new Central Committee during the 12th National Congress of the ruling Vietnam Communist Party in Hanoi, Vietnam, January 26, 2016. REUTERS/Kham

Vietnam's Deputy Prime Minister Nguyen Xuan Phuc (back) walks away as Prime Minister Nguyen Tan Dung (front) sits after voting for the new Central Committee during the 12th National Congress of the ruling Vietnam Communist Party in Hanoi, Vietnam, January 26, 2016. REUTERS/Kham 

Vietnam's Prime Minister Nguyen Tan Dung is seen after voting for the new Central Committee during the 12th National Congress of the ruling Vietnam Communist Party in Hanoi, Vietnam, January 26, 2016. REUTERS/Kham 

Vietnam Communist Party's General Secretary Nguyen Phu Trong (L) casts his ballots to vote for new Central Committee as President Truong Tan Sang (2nd L), Prime Minister Nguyen Tan Dung (2nd R) and National Assembly's Chairman Nguyen Sinh Hung stand behind him during the 12th National Congress of the ruling Vietnam Communist Party in Hanoi, Vietnam, January 26, 2016. REUTERS/Kham TPX IMAGES OF THE DAY

Vietnam Communist Party's General Secretary Nguyen Phu Trong (L) holds ballots to vote for new Central Committee as President Truong Tan Sang (C) and Prime Minister Nguyen Tan Dung follow during the 12th National Congress of the ruling Vietnam Communist Party in Hanoi, Vietnam, January 26, 2016. REUTERS/Kham

Vietnam Communist Party Secretary General Nguyen Phu Trong (L) and Prime Minister Nguyen Tan Dung walk on the podium during the official opening ceremony of the Vietnam Communist Party's 12th National Congress being held in Hanoi on January 21, 2016. REUTERS/Hoang Dinh Nam/Pool 

Reporters take photos of a video screen showing Vietnam's Prime Minister Nguyen Tan Dung delivering a speech during a the opening ceremony of the 12th National Congress of Vietnam's Communist Party in Hanoi, Vietnam January 21, 2016. REUTERS/Luong Thai Linh/Pool 

Vietnam's Prime Minister Nguyen Tan Dung arrives for the opening ceremony of the 12th National Congress of Vietnam's Communist Party in Hanoi, Vietnam, January 21, 2016. REUTERS/Kham 

Vietnam's President Truong Tan Sang (C) walks between Prime Minister Nguyen Tan Dung (front), Hanoi City's Party Chief Pham Quang Nghi (L top) and Defence Minister Phung Quang Thanh (R, top) at the opening ceremony of the 12th National Congress of Vietnam's Communist Party in Hanoi, Vietnam, January 21, 2016. REUTERS/Kham 

Vietnam's Prime Minister Nguyen Tan Dung (C) attends the opening ceremony of the 12th National Congress of Vietnam's Communist Party with Hanoi City's Party Chief Pham Quang Nghi (L) and Defence Minister Phung Quang Thanh in Hanoi, Vietnam, January 21, 2016. REUTERS/Kham 

Vietnam's Prime Minister Nguyen Tan Dung (R) and Nguyen Phu Trong, Vietnam Communist Party General Secretary, walk into the podium prior to the official opening ceremony of the VCP's 12th National Congress being held in Hanoi on January 21, 2016. REUTERS/Hoang Dinh Nam/Pool 

Vietnam's Prime Minister Nguyen Tan Dung (R), Vietnam Communist Party General Secretary Nguyen Phu Trong (C) and President Truong Tan Sang prepare to take their seats on the podium prior to the official opening ceremony of the VCP's 12th National Congress being held in Hanoi on January 21, 2016. REUTERS/Hoang Dinh Nam/Pool 

Vietnam's President Truong Tan Sang (C) walks past leaders at the opening ceremony of the 12th National Congress of Vietnam's Communist Party in Hanoi, Vietnam, January 21, 2016. People on the photo are: Communist Party Chief Nguyen Phu Trong (L, bottom), Ho Chi Minh City's Party Chief Le Thanh Hai (top, L), Hanoi City's Party Chief Pham Quang Nghi (C, top), Defence Minister Phung Quang Thanh (R, top) and Prime Minister Nguyen Tan Dung (R, bottom). REUTERS/Kham 

Vietnam's Prime Minister Nguyen Tan Dung (C, bottom) speaks during the opening ceremony of the 12th National Congress of Vietnam's Communist Party in Hanoi, Vietnam, January 21, 2016. Leaders on photo are: Vietnam's Communist Party Chief Nguyen Phu Trong (R, bottom), Ho Chi Minh City's Party Chief Le Thanh Hai (R, top), Hanoi City's Party Chief Pham Quang Nghi (2n L. top), Defence Minister Phung Quang Thanh (2nd R, top), Police Minister Tran Dai Quang (R, top) and Standing member of Secretariat Le Hong Anh (R, bottom). REUTERS/Kham 

Vietnam's General Secretary of the Communist Party Nguyen Phu Trong (C, bottom) and other leaders attend the opening ceremony of the 12th National Congress of Vietnam's Communist Party in Hanoi, Vietnam, January 21, 2016. L-R, top: Vice Chairwoman of National Assembly Tong Thi Phong, Ho Chi Minh City's Party Chief Le Thanh Hai and Hanoi City's Party Chief Pham Quang Nghi. L-R, bottom: President Truong Tan Sang, Party Chief Nguyen Phu Trong and Prime Minister Nguyen Tan Dung. REUTERS/Kham 

Vietnam's General Secretary of the Communist Party Nguyen Phu Trong (L) walks as Prime Minister Nguyen Tan Dung follows upon their arrival for the opening ceremony of the 12th National Congress of Vietnam's Communist Party in Hanoi, Vietnam, January 21, 2016. REUTERS/Kham TPX IMAGES OF THE DAY

Nguyen Phu Trong (C), Vietnam Communist Party Secretary General, greets delegates as he enters the main meeting hall before the official opening ceremony of the VCP's 12th National Congress being held in Hanoi on January 21, 2016. REUTERS / POOL / HOANG DINH Nam 

Nguyen Phu Trong (C), Vietnam Communist Party Secretary General, greets delegates as he enters the main meeting hall before the official opening ceremony of the VCP's 12th National Congress being held in Hanoi on January 21, 2016. REUTERS / POOL / HOANG DINH Nam 

Prime Minister Nguyen Tan Dung (R) and President Truong Tan Sang (L) greet delegates as Nguyen Phu Trong (C), Vietnam Communist Party Secretary General, takes his seat before the official opening ceremony of the VCP's 12th National Congress being held in Hanoi on January 21, 2016. REUTERS / POOL / HOANG DINH Nam 

Vietnam's Prime Minister Nguyen Tan Dung (C) arrives for the opening ceremony of the 12th National Congress of Vietnam's Communist Party (VCP) in Hanoi, Vietnam, January 21, 2016. REUTERS/Luong Thai Linh/Pool 

Vietnam's Prime Minister Nguyen Tan Dung arrives for the opening ceremony of the 12th National Congress of Vietnam's Communist Party (VCP) in Hanoi, Vietnam, January 21, 2016. REUTERS/Luong Thai Linh/Pool 

Vietnam's Prime Minister Nguyen Tan Dung (R) claps after delivering the introductory speech next to Nguyen Phu Trong (L), Vietnam Communist Party Secretary General, during the official opening ceremony of the VCP's 12th National Congress being held in Hanoi on January 21, 2016. REUTERS/Hoang Dinh Nam/Pool 

Vietnam's Prime Minister Nguyen Tan Dung (R) delivers the introductory speech next to Nguyen Phu Trong (L), Vietnam Communist Party Secretary General, during the official opening ceremony of the VCP's 12th National Congress being held in Hanoi on January 21, 2016. REUTERS/Hoang Dinh Nam/Pool 

Vietnam's Prime Minister Nguyen Tan Dung delivers the introductory speech during the official opening ceremony of the VCP's 12th National Congress being held in Hanoi on January 21, 2016. REUTERS/Hoang Dinh Nam/Pool 

Vietnamese Prime Minister Nguyen Tan Dung (L) sits after introducing Nguyen Phu Trong (R), Vietnam Communist Party Secretary General, to take the floor during the official opening ceremony of the VCP's 12th National Congress being held in Hanoi on January 21, 2016. REUTERS/Hoang Dinh Nam/Pool 

Vietnamese Prime Minister Nguyen Tan Dung (R) sits after introducing Nguyen Phu Trong (L), Vietnam Communist Party Secretary General, to take the floor during the official opening ceremony of the VCP's 12th National Congress being held in Hanoi on January 21, 2016. REUTERS/Hoang Dinh Nam/Pool 

Vietnamese Prime Minister Nguyen Tan Dung (R) sits after introducing Nguyen Phu Trong (L), Vietnam Communist Party Secretary General, to take floor during the official opening ceremony of the VCP's 12th National Congress being held in Hanoi on January 21, 2016. REUTERS/Hoang Dinh Nam/Pool 

Party Central Committee Secretariat Le Hong Anh (L), Minister of Public Security of Vietnam General Tran Dai Quang (back, C) and Prime Minister Nguyen Tan Dung (R) attend a wreath laying ceremony at the mausoleum of late Vietnamese President Ho Chi Minh prior to the 12th National Congress of Vietnam's Communist Party (VCP), in Hanoi, Vietnam January 20, 2016. REUTERS/Luong Thai Linh/Pool 

(L-R) Vietnam's Party Central Committee Secretariat Le Hong Anh, Prime Minister Nguyen Tan Dung, Vietnam Communist Party's Secretary General Nguyen Phu Trong attend a wreath laying ceremony at the mausoleum of Vietnamese late President Ho Chi Minh prior to The 12th National Congress of Vietnam's Communist Party (VCP), in Hanoi, Vietnam 20 January 2016. REUTERS/Luong Thai Linh/Pool 

(L-R) Vietnam's Prime Minister Nguyen Tan Dung, Vietnam Communist Party's General Secretary Nguyen Phu Trong, President Truong Tan Sang, National Assembly Chairman Nguyen Sinh Hung, Head of the PCC Commission for Organization To Huy Rua, Head of the Party Central Committee's Inspection Commission Ngo Van Du, Chairman of the Vietnam Fatherland Front Central Committee Nguyen Thien Nhan attend a wreath laying ceremony at the mausoleum of Vietnamese late President Ho Chi Minh prior to The 12th National Congress of Vietnam's Communist Party (VCP), in Hanoi, Vietnam 20 January 2016. REUTERS/Luong Thai Linh/Pool 

Vietnam's Prime Minister Nguyen Tan Dung (2-L), National Assembly Chairman Nguyen Sinh Hung (C), Vietnam Communist Party's General Secretary Nguyen Phu Trong (2-R), President Truong Tan Sang (R) attend a wreath laying ceremony at the mausoleum of Vietnamese late President Ho Chi Minh prior to The 12th National Congress of Vietnam's Communist Party (VCP), in Hanoi, Vietnam 20 January 2016. REUTERS/Luong Thai Linh/Pool 

(L-R) Vietnam Communist Party's General Secretary Nguyen Phu Trong, President Truong Tan Sang, Prime Minister Nguyen Tan Dung, National Assembly Chairman Nguyen Sinh Hung and other Politburo members attend a wreath laying ceremony at the mausoleum of Vietnamese late President Ho Chi Minh prior to The 12th National Congress of Vietnam's Communist Party (VCP), in Hanoi, Vietnam 20 January 2016. REUTERS/Luong Thai Linh/Pool 

Vietnam's Prime Minister Nguyen Tan Dung (2-L), Vietnam Communist Party's General Secretary Nguyen Phu Trong (C), President Truong Tan Sang (R) attend a wreath laying ceremony at the mausoleum of Vietnamese late President Ho Chi Minh prior to The 12th National Congress of Vietnam's Communist Party (VCP), in Hanoi, Vietnam 20 January 2016. REUTERS/Luong Thai Linh/Pool 

Vietnam Communist Party's General Secretary Nguyen Phu Trong (C), President Truong Tan Sang (C-R), Prime Minister Nguyen Tan Dung (back, L), National Assembly Chairman Nguyen Sinh Hung (back, R) attend a wreath laying ceremony at the mausoleum of Vietnamese late President Ho Chi Minh prior to The 12th National Congress of Vietnam's Communist Party (VCP), in Hanoi, Vietnam 20 January 2016. REUTERS/Luong Thai Linh/Pool 

(L-R) Vietnam's Prime Minister Nguyen Tan Dung, Vietnam Communist Party's General Secretary Nguyen Phu Trong, President Truong Tan Sang attend a wreath laying ceremony at the mausoleum of Vietnamese late President Ho Chi Minh prior to The 12th National Congress of Vietnam's Communist Party (VCP), in Hanoi, Vietnam 20 January 2016. REUTERS/Luong Thai Linh/Pool 

(Front L-R) Secretary of Ho Chi Minh City Party Committee Le Thanh Hai, Party Central Committee Secretariat Le Hong Anh, Prime Minister Nguyen Tan Dung, Vietnam Communist Party's General Secretary Nguyen Phu Trong, President Truong Tan Sang, National Assembly Chairman Nguyen Sinh Hung, Head of the PCC Commission for Organization To Huy Rua, Head of the Party Central Committee's Inspection Commission Ngo Van Du, Chairman of the Vietnam Fatherland Front Central Committee Nguyen Thien Nhan attend a wreath laying ceremony at the mausoleum of Vietnamese late President Ho Chi Minh prior to The 12th National Congress of Vietnam's Communist Party (VCP), in Hanoi, Vietnam 20 January 2016. REUTERS/Luong Thai Linh/Pool 

Vietnam Communist Party's General Secretary Nguyen Phu Trong (C) and Prime Minister Nguyen Tan Dung (back, C) attend a wreath laying ceremony at the mausoleum of Vietnamese late President Ho Chi Minh prior to the 12th National Congress of Vietnam's Communist Party (VCP), in Hanoi, Vietnam 20 January 2016. REUTERS/Luong Thai Linh/Pool 

(L-R) Vietnam's Party Central Committee Secretariat Le Hong Anh, Prime Minister Nguyen Tan Dung, Vietnam Communist Party's General Secretary Nguyen Phu Trong, President Truong Tan Sang, National Assembly Chairman Nguyen Sinh Hung attend a wreath laying ceremony at the mausoleum of Vietnamese late President Ho Chi Minh prior to the 12th National Congress of Vietnam's Communist Party (VCP), in Hanoi, Vietnam 20 January 2016. REUTERS/Luong Thai Linh/Pool 

(L-R) Vietnam's Prime Minister Nguyen Tan Dung, Vietnam Communist Party's General Secretary Nguyen Phu Trong, President Truong Tan Sang, National Assembly Chairman Nguyen Sinh Hung attend a wreath laying ceremony at the mausoleum of Vietnamese late President Ho Chi Minh prior to The 12th National Congress of Vietnam's Communist Party (VCP), in Hanoi, Vietnam 20 January 2016. REUTERS/Luong Thai Linh/Pool 

Vietnam Communist Party's General Secretary Nguyen Phu Trong (front L), President Truong Tan Sang (R), Prime Minister Nguyen Tan Dung (back, L), National Assembly Chairman Nguyen Sinh Hung (back, R) attend a wreath laying ceremony at the mausoleum of Vietnamese late President Ho Chi Minh prior to the 12th National Congress of Vietnam's Communist Party (VCP), in Hanoi, Vietnam 20 January 2016. REUTERS/Luong Thai Linh/Pool 

Vietnam's Planning and Investment Minister Bui Quang Vinh (L) gestures next to Prime Minister Nguyen Tan Dung while attending the Vietnam Development Partnership Forum in Hanoi, December 5, 2015. Vietnam's economy is expected to post annual growth of 6.55 percent this year, Prime Minister Nguyen Tan Dung said on Saturday at the forum, better than the 5.98 percent growth posted in 2014. REUTERS/Kham 

A general view of the Vietnam Development Partnership Forum in Hanoi, December 5, 2015. Vietnam's economy is expected to post annual growth of 6.55 percent this year, Prime Minister Nguyen Tan Dung said on Saturday at the forum, better than the 5.98 percent growth posted in 2014. REUTERS/Kham 

Vietnam's Prime Minister Nguyen Tan Dung (front L) sits next to World Bank’s Country Director for Vietnam Victoria Kwakwa at the Vietnam Development Partnership Forum in Hanoi, December 5, 2015. Vietnam's economy is expected to post annual growth of 6.55 percent this year, Prime Minister Nguyen Tan Dung said on Saturday at the forum, better than the 5.98 percent growth posted in 2014. REUTERS/Kham 

Vietnam's Industry and Trade Minister Vu Huy Hoang (bottom L), Vietnamese Prime Minister Nguyen Tan Dung (top L), European Commission President Jean-Claude Juncker (top R) and European Trade Commissioner Cecilia Malmstroem attend a signing ceremony in Brussels, Belgium, December 2, 2015. REUTERS/Eric Vidal 

(L to R) Vietnam's Industry and Trade Minister Vu Huy Hoang, Vietnamese Prime Minister Nguyen Tan Dung, European Commission President Jean-Claude Juncker and European Trade Commissioner Cecilia Malmstroem shake hands after signing an agreement in Brussels, Belgium, December 2, 2015. REUTERS/Eric Vidal 

European Commission President Jean-Claude Juncker welcomes Vietnamese Prime Minister Nguyen Tan Dung at the European Commission headquarters in Brussels, Belgium, December 2, 2015. REUTERS/Eric Vidal 

Vietnamese Prime Minister Nguyen Tan Dung speaks beside European Commission President Jean-Claude Juncker (not pictured) during a joint statement after a meeting at the European Commission headquarters in Brussels, Belgium, December 2, 2015. REUTERS/Eric Vidal 

European Commission President Jean-Claude Juncker (R) welcomes Vietnamese Prime Minister Nguyen Tan Dung at the European Commission headquarters in Brussels, Belgium, December 2, 2015. REUTERS/Eric Vidal 

European Commission President Jean-Claude Juncker (L) welcomes Vietnamese Prime Minister Nguyen Tan Dung at the European Commission headquarters in Brussels, Belgium, December 2, 2015. REUTERS/Eric Vidal