TEHRAN — President Putin of Russia met his Iranian counterpart today and implicitly warned America not to use a former Soviet republic to stage an attack on Iran. He also said nations shouldn’t pursue oil pipeline projects in the area if they weren’t backed by regional powers.

At a summit of the five nations that border the inland Caspian Sea, Mr. Putin said none of the nations’ territory should be used by any outside countries for use of military force against any nation in the region. It was a clear reference to long-standing rumors that America was planning to use Azerbaijan, a former Soviet republic, as a staging ground for any possible military action against Iran.

“We are saying that no Caspian nation should offer its territory to third powers for use of force or military aggression against any Caspian state,” Mr. Putin said.

President Ahmadinejad of Iran also underlined the need to keep outsiders away from the Caspian.

“All Caspian nations agree on the main issue — that all aspects related to this sea must be settled exclusively by littoral nations,” he said. “The Caspian Sea is an inland sea and it only belongs to the Caspian states, therefore only they are entitled to have their ships and military forces here.”

Mr. Putin, whose trip to Tehran is the first by a Kremlin leader since World War II, warned that energy pipeline projects crossing the Caspian could only be implemented if all five nations that border the Caspian support them.

Mr. Putin did not name any specific country, but his statement underlined Moscow’s strong opposition to American-backed efforts to build pipelines to deliver hydrocarbons to the West bypassing Russia.

“Projects that may inflict serious environmental damage to the region cannot be implemented without prior discussion by all five Caspian nations,” he said.

Other nations bordering the Caspian Sea and in attendance at the summit are: Kazakhstan, Turkmenistan, and Azerbaijan.

The legal status of the Caspian — believed to contain the world’s third-largest energy reserves — has been in limbo since the 1991 Soviet collapse, leading to tension and conflicting claims to seabed oil deposits.

Iran, which shared the Caspian’s resources equally with the Soviet Union, insists that each coastal nation receive an equal portion of the seabed. Russia, Azerbaijan, and Kazakhstan want the division based on the length of each nation’s shoreline, which would give Iran a smaller share.