Russia, Iran and other Caspian Sea countries strongly warned outside countries on Tuesday against using their territories for launching military action, but they failed to reach an agreement on ways to divide the sea's vast energy resources.

The declaration at the end of the summit of leaders from the five nations bordering the inland sea, including Russian President Vladimir Putin and Iranian President Mahmoud Ahmadinejad, did not name any countries but it was a clear reference to long-standing rumors that the U.S. might be planning to use Azerbaijan, a former Soviet republic, as a staging ground for any possible military action against Iran.

"The parties underline that under no circumstances would they allow other nations to use their territory for waging aggression or other military action against any of the parties," the declaration said.

The countries also offered a sign of support for Iran's disputed nuclear program, stressing that any country that is a signatory to the Nuclear Nonproliferation Treaty can "carry out research and can use nuclear energy for peaceful means without discrimination," according to the declaration.

Earlier Tuesday Putin, whose trip to Iran is the first by a Kremlin leader since World War II, warned that projects of energy pipelines crossing the Caspian could only be implemented if all five littoral nations support them.

Moscow has strong opposition to U.S.-backed efforts to build pipelines to deliver Central Asian and Caspian 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.

Iranian President Mahmoud Ahmadinejad 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."

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. Turkmenistan is also vying for the Caspian's resources.

The countries failed to reach agreement on dividing the Caspian, but they agreed to continue holding regular talks. Ahmadinejad said the next Caspian summit will be held next year in Baku, Azerbaijan.

Following the summit, Putin and Ahmadinejad went into talks. Putin indicated the meeting would touch on the Iran's disputed nuclear program, but he did not elaborate. Putin also planned to meet with Iran's Supreme Leader Ali Khamenei.

Putin's visit is taking place amid hopes that a round of personal diplomacy could help offer a solution to an international standoff on Iran's nuclear program.

The Russian leader's trip had been thrown into doubt when the Kremlin said Sunday that he had been informed by Russian special services that suicide attackers might try to kill him in Tehran, but he shrugged off the warning.

Iranian Foreign Ministry spokesman Mohammad Ali Hosseini called the reports disinformation spread by adversaries who hoped to spoil good relations between Russia and Iran.

Putin has warned the U.S. and other nations against trying to coerce Iran into reining in its nuclear program and insists peaceful dialogue is the only way to deal with Tehran's defiance of a U.N. Security Council demand that it suspend uranium enrichment.

Iran's rejection of the council's demand and its previous clandestine atomic work has fed suspicions in the U.S. and others that Tehran is secretly trying to develop nuclear weapons. Iran insists its program is for peaceful purposes, including generating electricity.

Putin underlined his disagreements with Washington last week, saying he saw no "objective data" to prove claims that Iran is trying to construct nuclear weapons. On Monday, he emphasized that he would negotiate in Tehran on behalf of the five permanent U.N. Security Council members and Germany, a group that has led efforts to resolve the stalemate with Tehran.

In Washington, State Department spokesman Tom Casey said the U.S. government expected Putin to "convey the concerns shared by all of us about the failure of Iran to comply with the international community's requirements concerning its nuclear program."

While the Kremlin has shielded Tehran from a U.S. push for a third round of U.N. sanctions, Iran has voiced annoyance about Moscow's foot-dragging in building a nuclear power plant in the southern port of Bushehr under a $1 billion (euro700,000) contract.

Russia has warned that the plant would not be launched this fall as planned because Iran was slow in making payments. Iranian officials have angrily denied any payment arrears and accused the Kremlin of caving in to Western pressure.

Moscow also has ignored Iranian demands to ship fuel for the plant, saying it would be delivered only six months before the Bushehr plant goes on line. The launch date has been delayed indefinitely amid the payment dispute.