The question whether the Caspian Sea is an ocean or a lake is set to determine the future of the vast body of landlocked water.
Leaders of the five countries along its shores have signed a convention aimed at ending decades-long uncertainty over exploitation of its resources.
The agreement signed 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.
And the lynchpin of the whole negotiations is whether the 370,000sqkm Caspian Sea is a sea or a lake, reports the BBC.
Iran has argued it should be called a lake, a description that has wide implications.
If it was termed a sea, it would be covered by the international maritime law, namely the United Nations Law of the Sea.
Under this binding legislation, any country can access the natural resources in the ocean.
But if it is defined as a lake, then it would have to be split equally between all five “littoral” countries – the ones that make up its shores.
The signed agreement gives the body of water a “special legal status”, which means it is neither a sea or lake, Russian officials said.
At stake are the Caspian’s vast oil and gas reserves.
Its seabed is estimated to hold 50 billion barrels of oil and almost 8.4 trillion cubic metres of natural gas.
This prize of vast resources has led to past bitter disputes – including the deployment of warships to deter contractors hired by rival companies.
The Caspian Sea is also the source of 90percent of the world’s caviar. It holds various species of the fish sturgeon that the delicacy is sourced from.
But in recent years stocks have plummeted due to overfishing. Kazakh President Nursultan Nazarbayev said on Sunday that the recent agreement allowed the setting of national quotas for fishing.
© Nine Digital Pty Ltd 2018