TEHRAN, Iran – Russian leader Vladimir Putin met his Iranian counterpart yesterday and implicitly warned the U.S. not to use a former Soviet republic to stage an attack on Iran. He also said countries bordering the Caspian Sea must jointly back any oil pipeline projects in the region.

At a summit of the five nations that border the inland Caspian Sea, 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 the U.S. 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,” Putin said.

Iranian President Mahmoud Ahmadinejad also underlined the need for solidarity.

“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,” he said.

A State Department spokesman, Tom Casey, said the United States is not planning military action against Iran.

“We are pursuing a diplomatic course with respect to Iran that includes with respect to its nuclear program as well as with respect to its support for terrorism and other issues that are out there,” he said.

Putin refused to set a date for the start-up of Iran’s first nuclear power plant, to be built by Russia.

“I only gave promises to my mom when I was a small boy,” Putin told Iranian reporters, when asked whether he could promise that the plant that Russia is building would be launched before his term ends next May.

At the same time, he said, “We are not going to renounce our obligations.”

Putin’s careful stance suggested that Russia is seeking to preserve solid ties with Iran without angering the West. A clear pledge by Putin to quickly finish the plant would embolden Iran and could complicate international talks on the nuclear standoff.

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 sea support them.

Putin did not name a specific country, but his statement underlined Moscow’s strong opposition to U.S.-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.