Saudi Arabia's Prince Abdullah Bin Faisal (C) listens as U.S. President Barack Obama speaks during the 71st United Nations General Assembly in Manhattan, New York, U.S. September 20, 2016. REUTERS/Lucas Jackson 

Crown Prince Muhammad bin Nayef of Saudi Arabia confers with a member of his delegation during a high-level meeting on addressing large movements of refugees and migrants at the United Nations General Assembly in Manhattan, New York, U.S., September 19, 2016. REUTERS/Lucas Jackson

Crown Prince Muhammad bin Nayef of Saudi Arabia confers with a member of his delegation during a high-level meeting on addressing large movements of refugees and migrants at the United Nations General Assembly in Manhattan, New York, U.S., September 19, 2016. REUTERS/Lucas Jackson

Crown Prince Muhammad bin Nayef of Saudi Arabia attends a high-level meeting on addressing large movements of refugees and migrants at the United Nations General Assembly in Manhattan, New York, U.S., September 19, 2016. REUTERS/Lucas Jackson

Crown Prince Muhammad bin Nayef of Saudi Arabia speaks during a high-level meeting on addressing large movements of refugees and migrants at the United Nations General Assembly in Manhattan, New York, U.S., September 19, 2016. REUTERS/Lucas Jackson

Crown Prince Muhammad bin Nayef of Saudi Arabia adjusts his head cover during a high-level meeting on addressing large movements of refugees and migrants at the United Nations General Assembly in Manhattan, New York, U.S., September 19, 2016. REUTERS/Lucas Jackson

Crown Prince Muhammad bin Nayef of Saudi Arabia confers with a member of his delegation during a high-level meeting on addressing large movements of refugees and migrants at the United Nations General Assembly in Manhattan, New York, U.S., September 19, 2016. REUTERS/Lucas Jackson

Saudi Arabia's Deputy Crown Prince Mohammed bin Salman reacts upon his arrival at the Elysee Palace in Paris, France in this June 24, 2015 file photo. Saudi Arabia plans to set up a $2 trillion megafund for post-oil era, Bloomberg reported on April 1, 2016, citing Saudi deputy crown prince Mohammed bin Salman. REUTERS/Charles Platiau/Files TPX IMAGES OF THE DAY

U.S. Vice President Joe Biden (R) offers his condolences to Prince Salman bin Abdel-Aziz (L), upon the death of on his brother Saudi Crown Prince Sultan bin Abdul-Aziz Al Saud, at Prince Sultan palace in Riyadh, October 27, 2011. REUTERS/Fahad Shadeed (SAUDI ARABIA - Tags: POLITICS ROYALS OBITUARY) 

U.S. Vice President Joe Biden (R) offers his condolences to Prince Salman bin Abdel-Aziz (L), upon the death of on his brother Saudi Crown Prince Sultan bin Abdul-Aziz Al Saud, at Prince Sultan palace in Riyadh, October 27, 2011. REUTERS/Fahad Shadeed (SAUDI ARABIA - Tags: POLITICS ROYALS OBITUARY) 

U.S. Senator John McCain (L-R), U.S. Vice President Joe Biden and Saudi Foreign Minister Prince Saud Al-Faisal meet at Riyadh airbase October 27, 2011. Biden led an American delegation to offer his condolences on the death of late Saudi Crown Prince Sultan bin Abdul-Aziz Al Saud. REUTERS/Fahad Shadeed (SAUDI ARABIA - Tags: POLITICS) 

U.S. Senator John McCain (L-R), U.S. Vice President Joe Biden and Saudi Foreign Minister Prince Saud Al-Faisal meet at Riyadh airbase October 27, 2011. Biden led an American delegation to offer his condolences on the death of late Saudi Crown Prince Sultan bin Abdul-Aziz Al Saud. REUTERS/Fahad Shadeed (SAUDI ARABIA - Tags: POLITICS) 

U.S. Vice President Joe Biden (R) and U.S. Senator John McCain arrive to offer their condolences on the death of the late Saudi Crown Prince Sultan bin Abdul-Aziz Al Saud at Riyadh airbase October 27, 2011. REUTERS/Fahad Shadeed (SAUDI ARABIA - Tags: POLITICS) 

U.S. Senator John McCain (L-R), U.S. Vice President Joe Biden and Saudi Foreign Minister Prince Saud Al-Faisal share a laugh as they meet at Riyadh airbase October 27, 2011. Biden led an American delegation to offer his condolences on the death of late Saudi Crown Prince Sultan bin Abdul-Aziz Al Saud. REUTERS/Fahad Shadeed (SAUDI ARABIA - Tags: POLITICS) 

U.S. Vice President Joe Biden walks with Saudi Foreign minister Prince Saud Al-Faisal upon his arrival at Riyadh airbase October 27, 2011. Biden led an American delegation to offer his condolences on the death of late Saudi Crown Prince Sultan bin Abdul-Aziz Al Saud. REUTERS/Fahad Shadeed (SAUDI ARABIA - Tags: POLITICS) 

U.S. Vice President Joe Biden arrives to offer his condolences on the death of the late Saudi Crown Prince Sultan bin Abdul-Aziz Al Saud at Riyadh airbase October 27, 2011. REUTERS/Fahad Shadeed (SAUDI ARABIA - Tags: POLITICS) 

U.S. Vice President Joe Biden (C) is greeted by Saudi Foreign Minister Price Saud Al-Faisal upon his arrival at Riyadh airbase October 27, 2011. Biden led an American delegation to offer his condolences on the death of late Saudi Crown Prince Sultan bin Abdul-Aziz Al Saud. At left is U.S. Senator John McCain. REUTERS/Fahad Shadeed (SAUDI ARABIA - Tags: POLITICS) 

U.S. Vice President Joe Biden arrives to offer his condolences on the death of the late Saudi Crown Prince Sultan bin Abdul-Aziz Al Saud at Riyadh airbase in Riyadh October 27, 2011. REUTERS/Fahad Shadeed (SAUDI ARABIA - Tags: POLITICS TRANSPORT) 

Riyadh Governor Prince Salman bin Abdul Aziz al-Saud (in car, L), brother of Crown Prince Sultan bin Abdulaziz al-Saud, who died in New York on Saturday, arrives at Al Oud cemetery in Riyadh October 25, 2011. The death of Saudi Arabia's Crown Prince Sultan sets the stage for an eventual generational shift in the ageing leadership of the world's top oil exporter, even if King Abdullah picks 77-year-old Prince Nayef to succeed him. REUTERS/Hamad I Mohammed (SAUDI ARABIA - Tags: ROYALS OBITUARY POLITICS) 

Riyadh Governor Prince Salman bin Abdul Aziz al-Saud (L) and other family members carry the body of Crown Prince Sultan bin Abdulaziz al-Saud, who died in America on Saturday, at Turki bin Abdullah Mosque after the funeral prayer in Riyadh October 25, 2011. The death of Saudi Arabia's Crown Prince Sultan sets the stage for an eventual generational shift in the ageing leadership of the world's top oil exporter, even if King Abdullah picks 77-year-old Prince Nayef to succeed him. REUTERS/Hamad I Mohammed (SAUDI ARABIA - Tags: ROYALS OBITUARY POLITICS) 

Prince Khaled bin Sultan bin Abdul-Aziz (R), the son of Saudi Crown Prince Sultan bin Abdulaziz al-Saud, who died on Saturday, arrives at funeral prayers in Turki bin Abdullah Mosque in Riyadh October 25, 2011. The death of Saudi Arabia's Crown Prince Sultan sets the stage for an eventual generational shift in the ageing leadership of the world's top oil exporter, even if King Abdullah picks 77-year-old Prince Nayef to succeed him. REUTERS/Hamad I Mohammed (SAUDI ARABIA - Tags: ROYALS OBITUARY POLITICS) 

Riyadh Governor Prince Salman bin Abdul Aziz al-Saud (centre L) and other family members carry the body of Crown Prince Sultan bin Abdulaziz al-Saud, who died in America on Saturday, at Turki bin Abdullah Mosque after the funeral prayer in Riyadh October 25, 2011. The death of Saudi Arabia's Crown Prince Sultan sets the stage for an eventual generational shift in the ageing leadership of the world's top oil exporter, even if King Abdullah picks 77-year-old Prince Nayef to succeed him. REUTERS/Hamad I Mohammed (SAUDI ARABIA - Tags: ROYALS OBITUARY POLITICS) 

Riyadh Governor Prince Salman bin Abdul Aziz al-Saud (2nd L) and other family members carry the body of Crown Prince Sultan bin Abdulaziz al-Saud, who died in America on Saturday, at Turki bin Abdullah Mosque after the funeral prayer in Riyadh October 25, 2011. The death of Saudi Arabia's Crown Prince Sultan sets the stage for an eventual generational shift in the ageing leadership of the world's top oil exporter, even if King Abdullah picks 77-year-old Prince Nayef to succeed him. REUTERS/Hamad I Mohammed (SAUDI ARABIA - Tags: ROYALS OBITUARY POLITICS) 

A signboard at New York Presbyterian Hospital is seen on the Upper East Side of Manhattan, July 29, 2011. Saudi Arabia's ailing Crown Prince Sultan bin Abdul Aziz has undergone an operation in a New York hospital, according to an official at the kingdom's consulate. REUTERS/Allison Joyce (UNITED STATES - Tags: HEALTH ROYALS) 

A signboard at New York Presbyterian Hospital is seen on the Upper East Side of Manhattan, July 29, 2011. Saudi Arabia's ailing Crown Prince Sultan bin Abdul Aziz has undergone an operation in a New York hospital, according to an official at the kingdom's consulate. REUTERS/Allison Joyce (UNITED STATES - Tags: HEALTH ROYALS) 

New York Presbyterian Hospital is seen on the Upper East Side of Manhattan, July 29, 2011. Saudi Arabia's ailing Crown Prince Sultan bin Abdul Aziz has undergone an operation in a New York hospital, according to an official at the kingdom's consulate. REUTERS/Allison Joyce (UNITED STATES - Tags: HEALTH ROYALS) 

A signboard at New York Presbyterian Hospital is seen on the Upper East Side of Manhattan, July 29, 2011. Saudi Arabia's ailing Crown Prince Sultan bin Abdul Aziz has undergone an operation in a New York hospital, according to an official at the kingdom's consulate. REUTERS/Allison Joyce (UNITED STATES - Tags: HEALTH ROYALS) 

Bridegrooms attend a mass wedding ceremony in Sanaa October 21, 2010. Some 3,200 brides and grooms were married in the wedding financed by Saudi Crown Prince Sultan Bin Abdul-Aziz. REUTERS/Khaled Abdullah (YEMEN - Tags: SOCIETY) 

Bridegrooms attend a mass wedding ceremony in Sanaa October 21, 2010. Some 3,200 brides and grooms were married in the wedding financed by Saudi Crown Prince Sultan Bin Abdul-Aziz. REUTERS/Khaled Abdullah (YEMEN - Tags: SOCIETY) 

Bridegrooms attend a mass wedding ceremony in Sanaa October 21, 2010. Some 3,200 brides and grooms were married in the wedding financed by Saudi Crown Prince Sultan Bin Abdul-Aziz. REUTERS/Khaled Abdullah (YEMEN - Tags: SOCIETY) 

Bridegrooms attend a mass wedding ceremony in Sanaa October 21, 2010. Some 3,200 brides and grooms were married in the wedding financed by Saudi Crown Prince Sultan Bin Abdul-Aziz. REUTERS/Khaled Abdullah (YEMEN - Tags: SOCIETY) 

Men perform traditional Baraa dance during a mass wedding ceremony for 3,200 brides and grooms in Sanaa October 21, 2010. The wedding was financed by Saudi Crown Prince Sultan Bin Abdul-Aziz. REUTERS/Khaled Abdullah (YEMEN - Tags: SOCIETY) 

Men perform traditional Baraa dance during a mass wedding ceremony for 3,200 brides and grooms in Sanaa October 21, 2010. The wedding was financed by Saudi Crown Prince Sultan Bin Abdul-Aziz. REUTERS/Khaled Abdullah (YEMEN - Tags: SOCIETY IMAGES OF THE DAY) 

U.S. Defence Secretary Robert Gates (L) meets with Saudi Crown Prince Sultan bin Abdul-Aziz in Riyadh March 10, 2010. REUTERS/Jim Watson/Pool (SAUDI ARABIA - Tags: POLITICS ROYALS) 

Spanish Princess Letizia (R), Spanish Crown Prince Felipe (2nd R) and Saudi Arabia's Crown Prince Sultan Bin Abdul aziz (2nd L) arrive for a luncheon at Madrid's Royal Palace June 6, 2008. REUTERS/Susana Vera(SPAIN) 

Spanish Crown Prince Felipe (L), Saudi Arabia's Crown Prince Sultan Bin Abdul aziz Al-Saud and Spanish Princess Letizia pose for photographers before a luncheon at Madrid's Royal Palace June 6, 2008. REUTERS/Susana Vera(SPAIN) 

Spanish Crown Prince Felipe (L), Saudi Arabia's Crown Prince Sultan Bin Abdul aziz Al-Saud and Spanish Princess Letizia pose for photographers before a luncheon at Madrid's Royal Palace June 6, 2008. REUTERS/Susana Vera(SPAIN) 

Saudi Crown Prince Sultan (R) and Saudi's Intelligence Chief Prince Mugrin bin Abdul-Aziz, brother of Saudi's King Abdullah, attend the opening ceremony of the Information Technology and National Security conference in Riyadh December 1, 2007. REUTERS/Ali Jarekji (SAUDI ARABIA) 

Saudi Crown Prince Sultan (R) and Saudi's Intelligence Chief Prince Muqrin bin Abdul-Aziz, brother of Saudi's King Abdullah, attend the opening ceremony of the Information Technology and National Security conference in Riyadh December 1, 2007. REUTERS/Ali Jarekji (SAUDI ARABIA) 

Saudi Crown Prince Sultan (L) is greeted by Intelligence Chief Prince Muqrin bin Abdul-Aziz, brother of Saudi's King Abdullah, on his arrival to the opening ceremony of the Information Technology and National Security conference in Riyadh December 1, 2007. REUTERS/Ali Jarekji (SAUDI ARABIA) 

Russia's President Vladimir Putin (R) meets Saudi Arabia's Crown Prince Sultan bin Abdul-Aziz in Moscow's Kremlin November 23, 2007. REUTERS/Sergei Karpukhin (RUSSIA) 

Saudi Arabian Crown Prince Sultan bin Abdul-Aziz passes by a uniformed guard as he meets Russia's President Vladimir Putin in Moscow's Kremlin November 23, 2007. REUTERS/Sergei Karpukhin (RUSSIA) 

Saudi Arabian Crown Prince Sultan bin Abdul-Aziz (R) passes by a uniformed guard in as he meets Russia's President Vladimir Putin in Moscow's Kremlin November 23, 2007. REUTERS/Sergei Karpukhin (RUSSIA) 

Russia's President Vladimir Putin (L) meets Saudi Arabian Crown Prince Sultan bin Abdul-Aziz in Moscow's Kremlin November 23, 2007. REUTERS/Sergei Karpukhin (RUSSIA) 

Russia's Foreign Minister Sergei Lavrov (L) meets Saudi Arabian Crown Prince Sultan bin Abdul-Aziz in Moscow November 23, 2007. REUTERS/Pool (RUSSIA) 

Russia's Foreign Minister Sergei Lavrov (L) meets Saudi Arabian Crown Prince Sultan bin Abdul-Aziz in Moscow November 23, 2007. REUTERS/Pool (RUSSIA) 

Russia's Foreign Minister Sergei Lavrov (L) meets Saudi Arabian Crown Prince Sultan bin Abdul-Aziz in Moscow November 23, 2007. REUTERS/Pool (RUSSIA) 

Saudi Arabian Crown Prince Sultan bin Abdul-Aziz inspects the honour guards after his arrival at Vnukovo airport in Moscow November 21, 2007. REUTERS/Denis Sinyakov (RUSSIA) 

Saudi Arabian Crown Prince Sultan bin Abdul-Aziz inspects the honour guards after his arrival at Vnukovo airport in Moscow November 21, 2007. REUTERS/Denis Sinyakov (RUSSIA) 

Saudi Arabian Crown Prince Sultan bin Abdul-Aziz arrives at Vnukovo airport in Moscow November 21, 2007. REUTERS/Denis Sinyakov (RUSSIA) 

Saudi Arabian Crown Prince Sultan bin Abdul-Aziz inspects the honour guards after his arrival at Vnukovo airport in Moscow November 21, 2007. REUTERS/Denis Sinyakov (RUSSIA) 

U.S. Vice President Dick Cheney (L) meets Saudi King Abdullah and Saudi Crown Prince Sultan bin Abdul Aziz Al Saud (R) at the Royal Palace in Tabuk May 12, 2007. REUTERS/Saudi News Agency/Handout (SAUDI ARABIA) QUALITY FROM SOURCE 

U.S. Vice President Dick Cheney (R) is welcomed by Saudi Crown Prince Sultan bin Abdul Aziz Al Saud (R) upon his arrival at King Faisal Airbase in Tabuk May 12, 2007. REUTERS/Saudi News Agency/Handout (SAUDI ARABIA) QUALITY FROM SOURCE 

U.S. Vice President Dick Cheney (L) is welcomed by Saudi Crown Prince Sultan bin Abdul Aziz Al Saud (R) upon his arrival at King Faisal Airbase in Tabuk May 12, 2007. REUTERS/Saudi News Agency/Handout (SAUDI ARABIA) QUALITY FROM SOURCE 

Japanese Prime Minister Shinzo Abe (L) is escorted by Saudi Crown Prince Sultan bin Abdul-Aziz (front R) upon his arrival in Riyadh April 28, 2007. REUTERS/Toshi Matsumoto/Pool (SAUDI ARABIA) 

Japanese Prime Minister Shinzo Abe (L) introduces Japan Business Federation (Keidanren) Chairman Fujio Mitarai (R) to Saudi Crown Prince Sultan bin Abdul-Aziz (2nd R) during a luncheon at the prince's palace in Riyadh April 28, 2007. REUTERS/Issei Kato (SAUDI ARABIA) 

Saudi Crown Prince Sultan bin Abdul-Aziz (R) speaks during a meeting with Japanese Prime Minister Shinzo Abe (L) at the former's palace in Riyadh April 28, 2007. REUTERS/Issei Kato (SAUDI ARABIA) 

Japanese Prime Minister Shinzo Abe (L) speaks during a meeting with Saudi Crown Prince Sultan bin Abdul-Aziz (R) at the latter's palace in Riyadh April 28, 2007. REUTERS/Issei Kato (SAUDI ARABIA) 

France's President Jacques Chirac (L) stands with Saudi Arabia'sCrown Prince Sultan bin Abdul Aziz on the steps of the Elysee Palace in Paris July 21, 2006. REUTERS/Benoit Tessier (FRANCE)