US Secretary of State Marco Rubio has expressed Washington’s strong support for the decades-old idea of diversifying Turkmenistan's natural gas exports via a pipeline that would be constructed across the Caspian Sea, according to a US State Department statement released on May 29.

The statement followed a meeting in the US capital between Rubio and Turkmenistan's top diplomat Rashid Meredov.

"Minister Meredov and Secretary Rubio discussed ways to expand cooperation in the areas of energy, security and trade," the State Department said.

Turkmenistan's official statement on the meeting did not mention the proposed Trans-Caspian gas pipeline proposal, though it referred to Meredov and Rubio discussing ways to further expand cooperation in the energy, security and trade sectors.

"During the meeting at the White House, the sides discussed the current state of Turkmen-American cooperation and the prospects for its development in various areas," the Ministry of Foreign Affairs of Turkmenistan said in its statement published on May 30.

Turkmenistan has never expressed any solid backing for a Trans-Caspian pipeline, though in recent years there have been indications that Ashgabat might be coming round to the idea, given the dangers of its near total reliance on China as a gas export market and the rising rivalry of Russia as a competitor for gas sales to the Chinese.

However, in April, Turkmenistan announced that it had inked a $6.4bn contract with China Petroleum Engineering (600339.SS) that will see the company develop the fourth phase of Turkmenistan's Galkynysh field, one of the largest gas ⁠fields in the world. That deal might indicate a further bet on more gas sales to China.

Rubio’s expressed support for a Trans-Caspian pipeline could be related to there being US investors who would hope to participate in building the infrastructure.

Another strong backer of the proposed pipeline is Turkey. Gas piped across the Caspian would almost certainly be forwarded to Turkey, which, though oil and gas poor itself, has ambitions to become a gas hub that would re-direct received gas from various markets to Europe and other buyers.

John Roberts , an energy security expert at UK-based consultancy Methinks, told Azatlyk that the renewed mention of the pipeline project by the US and Turkmenistan indicated the interest of both sides in it.

He was quoted as saying: "The US's focus on the Trans-Caspian makes sense in two ways. First, in the Trump era, it could be a real opportunity for American investment. Second, it improves Europe's overall energy security. This is interesting for European views, but I don't know how it relates to US views at the moment."

He added: "This is interesting for the Turkmen side, because it actually mentions energy diversification and shows that it is making efforts in this direction."

An added complication to any move to greenlight a project to build a Trans-Caspian pipeline could be a blocking manoeuvre by Russia, possibly backed by Iran. Moscow might be expected to argue that any plan to lay such a pipeline across the inland sea would need the backing of all five of its littoral states, namely Russia, Turkmenistan, Iran, Kazakhstan and Azerbaijan.