MOSCOW (AP) — Leaders of the five countries along the Caspian Sea have signed a convention aimed at ending decades-long uncertainty over exploitation of its resources.

The agreement signed Sunday in Aktau, Kazakhstan, by the presidents of Russia, Iran, Azerbaijan, Turkmenistan and Kazakhstan, establishes rules for declaring each country's territorial waters and fishing zones. But the issue of how the seabed, which contains rich oil fields, will be delineated between the countries remains subject to further negotiations.

Iranian President Hasan Rouhani, according to the news agency Interfax, says "this issue will be settled additionally in the course of agreements between the relevant parties."

The legal status of the Caspian Sea, the world's largest inland body of water, had been unresolved since the 1991 collapse of the Soviet Union.