The five parties to the Tehran Convention on the Caspian Sea were due to meet in Tehran in May, but because of the war the summit was rescheduled to August 23, 2026. Topping the agenda was the recession of the Caspian coastline, but the Ukrainian strike in July might topple that.
For most of modern history, Russia (or the Soviet Union) and Iran were the only two states with access to the Caspian Sea. Iran lost the right of shipping in the Treaty of Turkmenchay in 1828 but regained it in treaties in 1921 and 1940, following the collapse of the tsarist regime. After the fall of the Soviet Union, Azerbaijan, Kazakhstan, and Turkmenistan became coastal states, requiring a new arrangement.
For most of modern history, Russia (or the Soviet Union) and Iran were the only two states with access to the Caspian Sea.
In 2003, the five states reached the Framework Convention for the Protection of the Marine Environment of the Caspian Sea, or the Tehran Convention, which took effect in 2006. The agreement mostly concerned environmental issues but set the groundwork for future developments. In 2007, the parties reached a memorandum of understanding to not allow any outside state into the Caspian and to set maritime boundaries. Given Iran’s short coastline, critics blamed the Ahmadinejad administration for relinquishing older treaties they believed had granted Iran half of the Caspian Sea (a misreading of the previous agreements). Opposition leader and former crown prince Reza Pahlavi recently alluded to this ahistorical claim.
Following additional summits, the five parties signed a second treaty covering security measures in Aktau, Kazakhstan, in 2018. This agreement was unpopular among Iran’s principalists. Iran has abided by the terms of the Aktau Treaty, but the parliament never ratified it—the only party that failed to do so.
But after Ukraine on July 25, 2026, attacked an Iranian cargo vessel enroute to Russia, allegedly carrying arms, Iranian media reported on August 5 that President Masoud Pezeshkian sent the treaty to the parliament for ratification after eight years. Esmaeil Baghaei, spokesman for the Ministry of Foreign Affairs, explained that ratification could “prevent possible exploitations of a lack of a legal framework, especially interventions and exploitations by non-regional actors.” Pezeshkian’s decision and the upcoming summit have reopened discussions about the Caspian Sea.
Tasnim News, close with the Islamic Revolutionary Guard Corps, defended the agreement, noting that no treaty ever entitled Iran to half of the sea. Citing Iran’s former ambassador to Azerbaijan, the Islamic Republic News Agency echoed this sentiment, saying the agreement will strengthen Iran by providing a framework to prosecute military disagreements. In a separate editorial, the publication favored ratifying the Aktau Treaty to deny NATO and Israel access for submarine attacks.
Khabar Online, close with the principalists, questioned the agreement because it does not define the origin lines. With the free world’s considerations to reduce reliance on Persian Gulf petroleum, the editorial pointed out that the Caspian Sea could become a substitute for the Persian Gulf, reducing the importance of the Strait of Hormuz.
Nour News, close with the Supreme National Security Council, cited Kazem Gharib-Abadi, the special envoy for Caspian Sea at the Ministry of Foreign Affairs, who repeated the pro-treaty talking points, emphasizing that disagreements over national priorities regarding the Caspian should not prevent cooperation.
The coastline recession complicates vessels’ access to piers and requires ships to sail in shallow waters.
One disagreement concerns policies causing the sea to recede. Climate change and industrial and agricultural policies are affecting the Caspian’s coastline. In the Mazandaran province, for example, the coast has been receding 2 to 4 centimeters a year. Even state-affiliated media point to these challenges. The coastline recession complicates vessels’ access to piers and requires ships to sail in shallow waters. Russia and Iran are the primary guilty parties for draining groundwater in coastal areas and building dams that reduce water flow into the sea, and Kazakhstan and Azerbaijan have protested their policies.
The Iranian regime’s push to ratify the Aktau Treaty is partly a result of the Ukrainian strike. The argument that Israel might use the sea for a submarine attack, presumably through Azerbaijan, is fantastical but it exposes Iran’s paranoia and vulnerability in its north. The decision also stems from the U.S. blockade in Iran’s southern coasts, necessitating stability in the north.
Yet, disagreements persist. It is unfortunate that Kazakhstan and Azerbaijan thus far have blamed only Russia for environmental problems affecting the Caspian, when even Nour News has acknowledged the role of Iranian dams and groundwater extractions. The Trump administration has directed its diplomatic attention to the Caucuses and Central Asia, and should remind Azerbaijan, Kazakhstan, and Turkmenistan that much of the blame also lies with Iran.
