Trans-Caspian gas: the law is nearly ready, the buyers are not

For a quarter of a century the standard explanation for why no pipeline carries Turkmen gas across the Caspian to Azerbaijan has been legal: Russia and Iran would not allow it. That explanation is getting weaker. Iran is now moving to ratify the 2018 Convention on the Legal Status of the Caspian Sea, the last of the five littoral states to do so, and the most careful reading of that treaty gives neighbours a say over a pipeline’s environmental assessment but not a veto over the pipeline. At the same time, the war involving Iran this year has shown how exposed the only working route for Turkmen gas to Türkiye has been. Both developments make a Trans-Caspian link look more plausible than it did a year ago. Neither supplies what the project has always lacked, which is a buyer willing to sign for the gas for long enough to pay for the pipe.

The legal question is narrowing

The convention was signed in Aktau in August 2018. It allows the parties to lay trunk pipelines on the seabed on condition that the projects meet the environmental standards in the agreements they have joined, including the 2003 Tehran Convention on the Caspian marine environment and its protocols. The protocol that matters here, on environmental impact assessment in a transboundary context, was signed in Moscow on 20 July 2018, three weeks before the main treaty.

Sassan Seyrafi, an international lawyer at the University of Tehran, wrote in 2020 that Russia and Iran treated the assessment protocol as a precondition for signing the convention. His reading is that the protocol lets every Caspian state take part in the assessment of a project such as a Trans-Caspian pipeline, but does not make the project subject to their approval. That view, from a scholar in Tehran, matters because it is the legal core of the dispute: consultation, not consent.

The convention has not yet entered into force, because it requires all five ratifications. In 2026 President Masoud Pezeshkian’s government submitted it to parliament with single-urgency status. Hassan Ghashghavi, spokesman for parliament’s national security commission, said Iran was the only littoral state that had not yet approved it. Critics in Tehran argue that Iran should first fix its baselines, since a concave coastline leaves it at a disadvantage in any division of the seabed; the government answers that seabed boundaries will be settled in separate agreements. Parliament began its review in August.

What Moscow and Tehran have said

Russia and Iran have framed their objections in environmental terms. In 2019 Russia’s then prime minister, Dmitry Medvedev, said he was convinced that all major Caspian projects should undergo a thorough and impartial environmental evaluation involving specialists from all Caspian countries. Sergei Prikhodko, then first deputy prime minister, argued that the convention guaranteed each state’s right to take part in assessing cross-border activity at sea. Iranian officials have also cited commercial reasons. Behrouz Namdari of the National Iranian Gas Company said in 2019 that Iran was against any Trans-Caspian pipelines and was not interested in creating competitors. RFE/RL’s analysis at the time noted that neither state objected to other Caspian subsea lines or to Russia’s own pipelines under the Black and Baltic seas. The assessment protocol, which both states sought, gives them the formal channel for raising concerns; it does not, on Seyrafi’s reading, give them more.

Iran’s foreign ministry spokesman, Esmaeil Baghaei, has presented ratification as a way to complete the legal framework for the Caspian and to prevent interference by non-regional actors. That is a reminder that, for Tehran, the treaty is as much about security as about seabed rights, and that ratification would not end its interest in how a pipeline is assessed.

The route through Iran has proved fragile

Türkiye’s attempt to reach Turkmen gas without a Caspian pipeline was a swap: Turkmenistan sent gas into northern Iran, and Iran delivered the same volume to Türkiye. Deliveries began in March 2025. Cedigaz, an energy information group, records that they stopped later that year after new US and EU sanctions on Iran. Turkish officials have since called for a direct Caspian link instead. At a Baku energy event in June 2026, Türkiye’s energy minister, Alparslan Bayraktar, said: “Perhaps we are now at a point where everyone is ready to say yes.”

Türkiye’s own long-term contract for Iranian gas expired at the end of July 2026. Energy Intelligence reported in August that flows were expected to continue for now under a make-up clause in the old contract rather than under a new agreement. For Ankara, that is a stopgap. For Ashgabat, it confirms that any westward sale routed through Iran depends on decisions taken in Washington, Brussels and Tehran, not in Turkmenistan.

Why the commercial case is still thin

Washington has taken a clear position. After meeting Turkmenistan’s foreign minister, Rashid Meredov, on 29 May, Secretary of State Marco Rubio “expressed strong US support for diversifying Turkmenistan’s natural gas exports through Trans-Caspian routes”, according to the State Department. Support of that kind helps with finance and politics. It does not create demand.

The European Union is the market the pipeline was designed for, and its policy points in two directions. In December 2025 it decided to end imports of Russian gas by the end of 2027, which creates room for new suppliers. But Cedigaz notes that EU policy discourages new long-term contracts and large new gas infrastructure, in line with its decarbonisation goals. A pipeline of this kind is normally financed against exactly such contracts. Transport is also costly: Cedigaz puts the cost of moving Caspian gas at $40–50 per thousand cubic metres through the South Caucasus Pipeline, $107 through TANAP and $65 through TAP. Its best case is at most 10 bcm a year of Turkmen gas reaching Türkiye, with much smaller volumes reaching Europe.

Estimates of the project’s size vary because the proposals vary. The original 1999 design was for 32 bcm a year at a cost of more than $5bn. A smaller interconnector of 10–12 bcm has been costed at $500–800m in figures cited by RFE/RL. The smaller line is affordable. The question is who commits to the gas.

Ashgabat is still investing eastward

Turkmenistan’s own choices this year point east. In April it signed a $5.1bn, four-year contract with China’s CNPC for the next phase of the Galkynysh field, which RFE/RL links to an aim of shipping 65 bcm a year to China, against current exports of just over 30 bcm. Ashgabat’s public line on the Caspian route has been supportive but conditional. In February the former president and current chairman of the People’s Council, Gurbanguly Berdimuhamedov, told Al Arabiya that Turkmenistan supports the pipeline but that seabed delimitation issues with Azerbaijan must be resolved before work can begin, Reuters reported. When President Serdar Berdimuhamedov made a state visit to Baku on 22 June, the Turkmen government’s account of the talks mentioned electricity supplies, a Caspian–Black Sea transport corridor and Caspian cooperation, but not a gas pipeline.

That silence should not be over-read, since Turkmen communiqués are brief. But the constraint Gurbanguly Berdimuhamedov named is bilateral, between the two states that would build the line. It is not one that Russia or Iran controls.

What to watch

Three things will show whether 2026 changes the pattern. The first is the vote in Iran’s parliament: ratification would bring the convention and its pipeline provisions into force for all five states. The second is the high-level meeting of Caspian states that Ashgabat and Baku proposed for October at Avaza, where any language on delimitation, pipelines or environmental assessment will be the signal. The third, and the one that matters most, is a signed purchase or transit contract naming volumes, a buyer and a start date. Until that exists, the legal debate is a debate about a project nobody has yet agreed to pay for. For policymakers who want the route to happen, the useful work is less in rebutting Moscow and Tehran than in making the gas bankable.

Sources

• RFE/RL — Can the dream of a Trans-Caspian pipeline be revived? (10 June 2026)
• Central Eurasia Studies (University of Tehran) — Seyrafi, Submarine oil and gas pipelines under the Aktau Convention and the EIA Protocol to the Tehran Convention (2020)
• RFE/RL — Russia, Iran cite ‘ecological concerns’ in opposing Trans-Caspian pipeline (15 August 2019)
• Shabtabnews — Iran parliament begins review of Caspian Sea convention (6 August 2026)
• Cedigaz — Turkmenistan: a new pipeline gas supplier for the EU or not? (17 December 2025)
• Energy Intelligence — Iran will likely continue gas flows to Turkey after contract expiration (20 August 2026)
• Reuters via Baird Maritime — Turkmenistan aims to diversify vast gas exports, ex-leader says (23 February 2026)
• Government of Turkmenistan — State visit of the President of Turkmenistan to the Republic of Azerbaijan (22 June 2026)