The Iranian first vice-president made the remarks at a ceremony to mark inauguration of the first phase of Astara port in the Northern Gilan province on Tuesday.
"The Islamic Republic of Iran attaches great importance to the expansion of trade ties with the Caspian Sea littoral states," Rahimi said.
The Caspian Sea is the largest enclosed body of water on earth by area, variously classed as the world's largest lake or a full-fledged sea.
Caspian Sea littoral states consist of Iran, Russia, Kazakhstan, Turkmenistan and Azerbaijan. They have been debating their share in the Caspian Sea legal regime since the collapse of the Soviet Union in 1991.
Iran has underlined that all littoral states should have a fair and just share of the Caspian Sea in a bid to guarantee durable peace and stability in the region.
The Caspian Sea is estimated to contain between 17 billion and 33 billion barrels of proven oil reserves.
The Caspian Sea legal regime is based on two agreements signed between Iran and the former Union of Soviet Socialist Republics (USSR) in 1921 and 1940. Although under the international law, no state can defy any agreements, which came into being before its establishment, the three new littoral states, established after the collapse of the Soviet Union, do not recognize the prior treaties, triggering a debate on the future status of the sea.