Iranian President Hassan Rohani is scheduled to make an official visit to Russia next month to take part in a Caspian states summit.
Iran's Press TV said Rohani will arrive in the Russian city of Astrakhan on September 29 for the fourth meeting of leaders of Caspian littoral states of Azerbaijan, Iran, Kazakhstan, Russia, and Turkmenistan.
The water boundaries of the Caspian Sea are disputed among the littoral states as each country seeks to develop the oil and natural gas resources under the sea.
Previous Caspian Sea summits have failed to resolve the border issues.
Iranian Foreign Minister Mohammad Javad Zarif will reportedly also visit Moscow on September 29 at the invitation of Russian Foreign Minister Sergei Lavrov.