Russian President Vladimir Putin said in Tehran on Tuesday no Caspian Sea state should let its soil be used to attack a fellow coastal state, in an apparent response to talk in the West about military strikes on Iran.

Iran is embroiled in a nuclear standoff with Western nations who accuse Tehran of seeking to develop nuclear weapons, and Washington has refused to rule out the use of military action if diplomacy fails resolve the row.

Putin's visit to attend a summit of five state surrounding the Caspian Sea, including Iran,  has been closely watched because of Russia's role as a mediator in the standoff with six world powers.

"We should not even think of making use of force in this region," Putin told a summit of the five Caspian Sea countries held in Iran, which is defying Western pressure to halt its sensitive nuclear programme.

"We need to agree that using the territory of one Caspian Sea (state) in the event of aggression against another is impossible," he told the other leaders at the start of the one-day meeting in the Iranian capital.

His comments on use of territory appear directed towards close US allies, Azerbaijan which borders the Caspian and near neighbour Turkey.

Putin is making the first trip by a Kremlin leader since 1943 after shrugging off a report about plot to assassinate him that led Russian officials to cast doubt on the trip. Iran dismissed the report as baseless.

Iran has refused to give up nuclear work Tehran says it needs to master so it can make electricity. The West says Iran's goal is atomic bombs and the United States has said it will not rule out military action if diplomacy fails. - Reuters