A man walks past boards with portraits of Afghan President Ashraf Ghani, Turkmen President Kurbanguly Berdymukhamedov and Pakistani Prime Minister Shahid Khaqan Abbasi during the launching ceremony of construction work of the TAPI project on the Afghan section of a natural gas pipeline that will link Turkmenistan through Afghanistan to Pakistan and India, near the town of Serhetabat, Turkmenistan February 23, 2018. REUTERS/Marat Gurt

People sit inside the terminal of the newly built airport with a screen showing a portrait of Turkmen President Kurbanguly Berdymukhamedov during its official opening in Ashgabat, Turkmenistan, September 17, 2016. REUTERS/Marat Gurt

People stay in front of the terminal of the newly built airport with a portrait of Turkmen President Kurbanguly Berdymukhamedov seen in the background during its official opening in Ashgabat, Turkmenistan, September 17, 2016. REUTERS/Marat Gurt

Afghanistan's President Ashraf Ghani (R) shakes hands with Turkmenistan's President Gurbanguly Berdymukhamedov after a news conference in Kabul, Afghanistan August 27, 2015. REUTERS/Omar Sobhani

Afghanistan's President Ashraf Ghani (2nd R) signs an agreement with Turkmenistan's President Gurbanguly Berdymukhamedov during a news conference in Kabul, Afghanistan August 27, 2015. REUTERS/Omar Sobhani

Afghanistan's President Ashraf Ghani (R) and Turkmenistan's President Gurbanguly Berdymukhamedov attend a news conference in Kabul, Afghanistan August 27, 2015. REUTERS/Omar Sobhani

Afghanistan's President Ashraf Ghani (R) and Turkmenistan's President Gurbanguly Berdymukhamedov attend a news conference in Kabul, Afghanistan August 27, 2015. REUTERS/Omar Sobhani

Turkmenistan's President Kurbanguly Berdymukhamedov (2nd L) and Afghanistan's Foreign Minister Salahuddin Rabbani (R) walk during an arrival ceremony at Hamid Karzai International Airport in Kabul, Afghanistan August 27, 2015. REUTERS/Mohammad Ismail

Members of the Afghan honor guard wait for Turkmenistan's President Kurbanguly Berdymukhamedov during an arrival ceremony at Hamid Karzai International Airport in Kabul, Afghanistan August 27, 2015. REUTERS/Mohammad Ismail

Turkmenistan's President Kurbanguly Berdymukhamedov speaks at a news briefing in Tbilisi, Georgia, July 2, 2015. REUTERS/David Mdzinarishvili

Turkmenistan's President Kurbanguly Berdymukhamedov speaks at a news briefing in Tbilisi, Georgia, July 2, 2015. REUTERS/David Mdzinarishvili

Turkmenistan's President Kurbanguly Berdymukhamedov speaks at a news briefing in Tbilisi, Georgia, July 2, 2015. REUTERS/David Mdzinarishvili

Turkmenistan's President Kurbanguly Berdymukhamedov speaks at a news briefing in Tbilisi, Georgia, July 2, 2015. REUTERS/David Mdzinarishvili

Georgia's President Georgy Margvelashvili (R) and his Turkmenistan's counterpart Kurbanguly Berdymukhamedov shake hands during their meeting in Tbilisi, Georgia, July 2, 2015. REUTERS/David Mdzinarishvili

Georgia's President Georgy Margvelashvili (L) and his Turkmenistan's counterpart Kurbanguly Berdymukhamedov walk past honour guards during a welcoming ceremony in Tbilisi, Georgia, July 2, 2015. REUTERS/David Mdzinarishvili

Georgia's President Georgy Margvelashvili (L) and his Turkmenistan's counterpart Kurbanguly Berdymukhamedov walk past honour guards during a welcoming ceremony in Tbilisi, Georgia, July 2, 2015. REUTERS/David Mdzinarishvili

Turkmenistan's President Kurbanguly Berdymukhamedov looks on during a welcoming ceremony in Tbilisi, Georgia, July 2, 2015. REUTERS/David Mdzinarishvili

People attend a ceremony to open a park, with a marble arch and a huge portrait of Turkmen President Kurbanguly Berdymukhamedov seen in the background, in Ashgabat, Turkmenistan, June 29, 2015. Turkmenistan, which rights groups view as one of the most repressive countries in the world, celebrated Berdymukhamedov's 58th birthday on Monday by opening a park in the capital Ashgabat bearing his name. The park features a large marble arch with a huge portrait of Berdymukhamedov wearing a traditional Turkmen hat and tunic. REUTERS/Marat Gurt

People gather in front of a monument to Turkmenistan's President Kurbanguly Berdymukhamedov during its inauguration ceremony in Ashgabat, Turkmenistan, May 25, 2015. Turkmenistan unveiled the first monument to Berdymukhamedov on Monday - a gilded 6-meter-high statue of the leader on horseback perched on a white cliff, reflecting his flourishing personality cult in the reclusive gas-rich nation. REUTERS/Marat Gurt TPX IMAGES OF THE DAY

A woman registers for voting in a parliamentary Election in Ashgabat December 15, 2013. Turkmenistan holds its first multi-party parliamentary election in its post-Soviet history on Sunday with all the candidates running on the same political line as strongman leader President Kurbanguly Berdymukhamedov. REUTERS/Marat Gurt (TURKMENISTAN - Tags: POLITICS ELECTIONS)

A woman casts her vote in a ballot box during voting in a parliamentary Election in Ashgabat December 15, 2013. Turkmenistan holds its first multi-party parliamentary election in its post-Soviet history on Sunday with all the candidates running on the same political line as strongman leader President Kurbanguly Berdymukhamedov. REUTERS/Marat Gurt (TURKMENISTAN - Tags: POLITICS ELECTIONS)

A man performs at the opening ceremony of a yacht club, which is part of the Avaza resort, on the Caspian Sea in western Turkmenistan June 29, 2013. Turkmen President Kurbanguly Berdymukhamedov, who wields virtually unlimited powers, wants to build a Las Vegas-style resort on the windswept shores of the Caspian Sea. REUTERS/Marat Gurt (TURKMENISTAN - Tags: SOCIETY TRAVEL WEALTH ENTERTAINMENT)

Artists hanging on ropes perform at the opening ceremony of a yacht club, which is part of the Avaza resort, on the Caspian Sea in western Turkmenistan June 29, 2013. Turkmen President Kurbanguly Berdymukhamedov, who wields virtually unlimited powers, wants to build a Las Vegas-style resort on the windswept shores of the Caspian Sea. REUTERS/Marat Gurt (TURKMENISTAN - Tags: SOCIETY TRAVEL WEALTH ENTERTAINMENT)

Seamen attend the opening ceremony of a hotel, which is part of the Avaza resort, on the Caspian Sea in western Turkmenistan June 28, 2013. Turkmen President Kurbanguly Berdymukhamedov, who wields virtually unlimited powers, wants to build a Las Vegas-style resort on the windswept shores of the Caspian Sea. REUTERS/Marat Gurt (TURKMENISTAN - Tags: SOCIETY TRAVEL WEALTH)

A portrait of Turkmen President Kurbanguly Berdymukhamedov is seen (rear) as guests applaud during the opening ceremony of a hotel, which is part of Avaza resort, on the Caspian sea in western Turkmenistan June 28, 2013. Berdymukhamedov, who wields virtually unlimited powers, wants to build a Las Vegas-style resort on the windswept shores of the Caspian Sea. REUTERS/Marat Gurt (TURKMENISTAN - Tags: TRAVEL SOCIETY WEALTH)

Artists perform during the opening ceremony of a hotel, which is part of the Avaza resort, on the Caspian sea in western Turkmenistan June 28, 2013. Turkmen President Kurbanguly Berdymukhamedov, who wields virtually unlimited powers, wants to build a Las Vegas-style resort on the windswept shores of the Caspian Sea. REUTERS/Marat Gurt (TURKMENISTAN - Tags: BUSINESS SOCIETY TRAVEL WEALTH)

Turkmenistan's President Kurbanguly Berdymukhamedov stands during a photo opportunity at an official visit to the United Nations European headquarters in Geneva October 9, 2012. REUTERS/Denis Balibouse (SWITZERLAND - Tags: POLITICS)

Turkmenistan's President Kurbanguly Berdymukhamedov stands during a photo opportunity at an official visit to the United Nations European headquarters in Geneva October 9, 2012. REUTERS/Denis Balibouse (SWITZERLAND - Tags: POLITICS HEADSHOT)

Turkmenistan's President Kurbanguly Berdymukhamedov stands during a photo opportunity at an official visit to the United Nations European headquarters in Geneva October 9, 2012. REUTERS/Denis Balibouse (SWITZERLAND - Tags: POLITICS HEADSHOT)

Turkmenistan's President Kurbanguly Berdymukhamedov attends a ceremony during an official visit to Switzerland at the government's guesthouse Lohn in the village of Kehrsatz, near the Swiss capital of Bern, October 8 , 2012. REUTERS/Pascal Lauener (SWITZERLAND - Tags: POLITICS)

Swiss President Eveline Widmer-Schlumpf (L) and Turkmenistan's President Kurbanguly Berdymukhamedov attend a ceremony during an official visit at the government's guesthouse Lohn in the village of Kehrsatz, near the Swiss capital of Bern, October 8 , 2012. REUTERS/Pascal Lauener (SWITZERLAND - Tags: POLITICS)

Swiss President Eveline Widmer-Schlumpf (L) welcomes Turkmenistan's President Kurbanguly Berdymukhamedov during an official visit at the government's guesthouse Lohn in the village of Kehrsatz, near the Swiss capital of Bern, October 8 , 2012. REUTERS/Pascal Lauener (SWITZERLAND - Tags: POLITICS)

Swiss President Eveline Widmer-Schlumpf (R) and Turkmenistan's President Kurbanguly Berdymukhamedov attend a ceremony during an official visit at the government's guesthouse Lohn in the village of Kehrsatz, near the Swiss capital of Bern, October 8 , 2012. REUTERS/Pascal Lauener (SWITZERLAND - Tags: POLITICS)

Turkmenistan's President Kurbanguly Berdymukhamedov inspect a guard of honour during an official visit to Switzerland at the government's guesthouse Lohn in the village of Kehrsatz, near the Swiss capital of Bern, October 8 , 2012. REUTERS/Pascal Lauener (SWITZERLAND - Tags: POLITICS)

Swiss President Eveline Widmer-Schlumpf (L) and Turkmenistan's President Kurbanguly Berdymukhamedov inspect a guard of honour during an official visit at the government's guesthouse Lohn in the village of Kehrsatz, near the Swiss capital of Bern, October 8 , 2012. REUTERS/Pascal Lauener (SWITZERLAND - Tags: POLITICS)

Swiss President Eveline Widmer-Schlumpf (L) and Turkmenistan's President Kurbanguly Berdymukhamedov inspect a guard of honour during an official visit at the government's guesthouse Lohn in the village of Kehrsatz, near the Swiss capital of Bern, October 8 , 2012. REUTERS/Pascal Lauener (SWITZERLAND - Tags: POLITICS TPX IMAGES OF THE DAY)

Women wearing traditional dresses, welcome voters with refreshments at a polling station in Ashgabat February 12, 2012. Turkmenistan votes on Sunday in a one-sided election certain to extend the rule of President Kurbanguly Berdymukhamedov over a Central Asian country holding 4 percent of global gas reserves, which rights groups rank among the world's most repressive. REUTERS/Marat Gurt (TURKMENISTAN - Tags: POLITICS ELECTIONS ENERGY)

A woman fills out her voting papers at a polling station in Ashgabat February 12, 2012. Turkmenistan votes on Sunday in a one-sided election certain to extend the rule of President Kurbanguly Berdymukhamedov over a Central Asian country holding 4 percent of global gas reserves, which rights groups rank among the world's most repressive. REUTERS/Marat Gurt (TURKMENISTAN - Tags: POLITICS ELECTIONS)

A man casts his vote into a ballot box at a polling station in Abadan, some 20 kilometres (12 miles) from capital Ashgabat February 12, 2012. Turkmenistan votes on Sunday in a one-sided election certain to extend the rule of President Kurbanguly Berdymukhamedov over a Central Asian country holding 4 percent of global gas reserves, which rights groups rank among the world's most repressive. REUTERS/Marat Gurt (TURKMENISTAN - Tags: ELECTIONS POLITICS)

A woman casts her vote into a ballot box at a polling station in Ashgabat February 12, 2012. Turkmenistan votes on Sunday in a one-sided election certain to extend the rule of President Kurbanguly Berdymukhamedov over a Central Asian country holding 4 percent of global gas reserves, which rights groups rank among the world's most repressive. REUTERS/Marat Gurt (TURKMENISTAN - Tags: ELECTIONS POLITICS)

Turkmenistan President Kurbanguly Berdymukhamedov (L) listens to Chinese Premier Wen Jiabao speak during their meeting in Beijing November 23, 2011. Berdymukhamedov is in China on an official visit from November 22 to 25. REUTERS/David Gray (CHINA - Tags: POLITICS)

Turkmenistan President Kurbanguly Berdymukhamedov (L) shakes hands with Chinese Premier Wen Jiabao in Beijing November 23, 2011. Berdymukhamedov is in China on an official visit from November 22 to 25. REUTERS/David Gray (CHINA - Tags: POLITICS)

Turkmenistan President Kurbanguly Berdymukhamedov (L) shakes hands with Chinese Premier Wen Jiabao in Beijing November 23, 2011. Berdymukhamedov is in China on an official visit from November 22 to 25. REUTERS/David Gray (CHINA - Tags: POLITICS)

Turkmenistan President Kurbanguly Berdymukhamedov (L) shakes hands with Chinese Premier Wen Jiabao in Beijing November 23, 2011. Berdymukhamedov is in China on an official visit from November 22 to 25. REUTERS/David Gray (CHINA - Tags: POLITICS)

Turkmenistan's President Kurbanguly Berdymukhamedov (L) celebrates by touching his champagne glass with that of Chinese President Hu Jintao after a signing ceremony in the Great Hall of the People in Beijing November 23, 2011. Berdymukhamedov is in China on an official visit from November 22 to 25. REUTERS/David Gray (CHINA - Tags: POLITICS)

Turkmenistan's President Kurbanguly Berdymukhamedov (L) drinks champagne with his Chinese counterpart Hu Jintao as they celebrate after a signing ceremony in the Great Hall of the People in Beijing November 23, 2011. Berdymukhamedov is in China on an official visit from November 22 to 25. REUTERS/David Gray (CHINA - Tags: POLITICS)

Turkmenistan's President Kurbanguly Berdymukhamedov (L) celebrates by touching his champagne glass with that of Chinese President Hu Jintao after a signing ceremony in the Great Hall of the People in Beijing November 23, 2011. Berdymukhamedov is in China on an official visit from November 22 to 25. REUTERS/David Gray (CHINA - Tags: POLITICS)

Turkmenistan's President Kurbanguly Berdymukhamedov (C) inspects a guard of honour with his Chinese counterpart Hu Jintao during an official welcoming ceremony in the Great Hall of the People in Beijing November 23, 2011. Berdymukhamedov is in China on an official visit from November 22 to 25. REUTERS/David Gray (CHINA - Tags: POLITICS)

Turkmenistan's President Kurbanguly Berdymukhamedov (C) inspects a guard of honour with his Chinese counterpart Hu Jintao during an official welcoming ceremony in the Great Hall of the People in Beijing November 23, 2011. Berdymukhamedov is in China on an official visit from November 22 to 25. REUTERS/David Gray (CHINA - Tags: POLITICS)

Turkmenistan's President Kurbanguly Berdymukhamedov (C) inspects a guard of honour with his Chinese counterpart Hu Jintao during an official welcoming ceremony in the Great Hall of the People in Beijing November 23, 2011. Berdymukhamedov is in China on an official visit from November 22 to 25. REUTERS/David Gray (CHINA - Tags: POLITICS)

Turkmenistan's President Kurbanguly Berdymukhamedov (L) is asked to inspect a guard of honour by his Chinese counterpart Hu Jintao during an official welcoming ceremony in the Great Hall of the People in Beijing November 23, 2011. Berdymukhamedov is in China on an official visit from November 22 to 25. REUTERS/David Gray (CHINA - Tags: POLITICS)

Turkmenistan's President Kurbanguly Berdymukhamedov (L) listens to his country's national anthem with his Chinese counterpart Hu Jintao during an official welcoming ceremony in the Great Hall of the People in Beijing November 23, 2011. Berdymukhamedov is in China on an official visit from November 22 to 25. REUTERS/David Gray (CHINA - Tags: POLITICS)

Turkmenistan's President Kurbanguly Berdymukhamedov (C) inspects a guard of honour with his Chinese counterpart Hu Jintao during an official welcoming ceremony in the Great Hall of the People in Beijing November 23, 2011. Berdymukhamedov is in China on an official visit from November 22 to 25. REUTERS/David Gray (CHINA - Tags: POLITICS)

Organization for Security and Co-operation in Europe Secretary General Lamberto Zannier gestures during a news conference in Moscow October 4, 2011. Zannier said on Tuesday that Turkmenistan's incumbent President Kurbanguly Berdymukhamedov?s statement that opposition representatives could take part in forthcoming elections ?goes in the right direction?. REUTERS/Sergei Karpukhin (RUSSIA - Tags: ELECTIONS POLITICS)

Organization for Security and Co-operation in Europe Secretary General Lamberto Zannier gestures during a news conference in Moscow October 4, 2011. Zannier said on Tuesday that Turkmenistan's incumbent President Kurbanguly Berdymukhamedov?s statement that opposition representatives could take part in forthcoming elections ?goes in the right direction?. REUTERS/Sergei Karpukhin (RUSSIA - Tags: ELECTIONS POLITICS HEADSHOT)

Russia's President Dmitry Medvedev, Tajikistan's President Imomali Rakhmon, Kazakhstan's President Nursultan Nazarbayev, Armenia's President Serzh Sarksyan and Turkmenistan's President Kurbanguly Berdymukhamedov (L-R) enter the hall for the Commonwealth of Independent States summit in the presidential residence Gorki outside Moscow May 8, 2010. REUTERS/Alexander Natruskin (RUSSIA - Tags: POLITICS)

EDITORS' NOTE: Reuters and other foreign media are subject to Iranian restrictions on their ability to film or take pictures in Tehran.

Tajikistan's President Imomali Rakhmon, Afghanistan's President Hamid Karzai, Iran's President Mahmoud Ahmadinejad, Iraq's President Jalal Talabani and Turkmenistan's President Kurbanguly Berdymukhamedov (L-R) attend celebrations for Nowrouz or the Iranian New Year in Tehran March 27, 2010. REUTERS/Raheb Homavandi (IRAN POLITICS)

Turkmenistan's President Kurbanguly Berdymukhamedov (L) is welcomed by France's President Nicolas Sarkozy at the Elysee Palace in Paris February 1, 2010. REUTERS/Philippe Wojazer (REUTERS - Tags: POLITICS)

Turkmen President Kurbanguly Berdymukhamedov (L) speaks with his Ukrainian counterpart Viktor Yushchenko during their meeting in Ashgabat September 15, 2009. Turkmenistan and Ukraine plan more talks on natural gas supply after the presidents of the two ex-Soviet countries met on Tuesday, five months after a pipeline blast cut off supplies of Turkmen gas to Russia and beyond. REUTERS/Pool/Mykola Lazarenko (TURKMENISTAN POLITICS ENERGY BUSINESS)

Turkmen President Kurbanguly Berdymukhamedov (R) shakes hands with his Ukrainian counterpart Viktor Yushchenko during their meeting in Ashgabat September 15, 2009. Turkmenistan and Ukraine plan more talks on natural gas supply after the presidents of the two ex-Soviet countries met on Tuesday, five months after a pipeline blast cut off supplies of Turkmen gas to Russia and beyond. REUTERS/Pool/Mykola Lazarenko (TURKMENISTAN POLITICS ENERGY)