The status of the Caspian Sea has long been under discussion among the five nations - Iran, Russia, Turkmenistan, Kazakhstan and Azerbaijan. The Russian Foreign Ministry said Monday the summit, which will be attended by Russian President Vladimir Putin, was expected to yield a political declaration that could act as a guideline until the approval of a convention on the legal status of the sea.
The summit held at the Sadabad Palace, a former residence of an Iranian shah, in northern Tehran was preceded by an official meeting ceremony between Putin and his Iranian counterpart Mahmoud Ahmadinejad.
The first summit in Ashgabat, Turkmenistan, in 2002 addressed the legal rights of Caspian nations to explore the huge oil reserves beneath the world's largest saline lake.
The issue of dividing the Caspian Sea emerged after the collapse of the Soviet Union in 1991. Until then, it was regulated by treaties between two littoral states - Iran and the U.S.S.R.