The status of the inland sea has been a source of long-running disagreements between the five littoral states - Azerbaijan, Iran, Kazakhstan, Russia, and Turkmenistan - since the collapse of the Soviet Union in 1991.
"Russia's position is that until we produce a new convention the agreements that are still valid between the Soviet Union and Iran will remain in force," said Alexander Golovin, the Foreign Ministry's special envoy, who headed the Russian delegation at a regular meeting of the Caspian working group in Tehran.
Under the 1921 and 1940 treaties between the Soviet Union and Iran, no borders were ever established. Moreover, the treaties related to shipping and fishing regulations, without covering oil and gas exploration.
Gololvin reiterated Russia's opposition to the introduction of unilateral demarcation lines, zones and borders on the Caspian.
Iran has insisted it will not sign any agreements on the status of the oil-rich sea until its national interests in the region are fully safeguarded. Iran, whose portion makes up only 14% of the Caspian shoreline, is demanding 20% of the sea.
At a summit in Tehran in October 2007, Caspian leaders failed to make any headway in resolving the dispute, but adopted a joint political declaration promoting efforts to build and enhance mutual confidence, regional security, and stability, and to refrain from the use of force in solving mutual problems.
The Caspian leaders are expected to hold the next summit in Baku later this year.