Caspian Sea states declared in Tehran today that they would not let their territory be used for an attack on any of them.
The declaration came at a summit in Iran of heads of countries in the region and was an apparent response to speculation the United States could resort to force in its nuclear row with Iran.
Washington has refused to rule out military action if diplomacy fails to resolve the row with Western nations, who accuse Iran of seeking atomic weapons, a charge Tehran denies
Iran, Russia, Kazakhstan, Azerbaijan and Turkmenistan said "under no circumstances will they allow (the use of their) territories by third countries to launch aggression or other military action against any of the member states".
They also acknowledged the rights of all signatories to the Non-Proliferation Treaty - which includes Iran - to develop peaceful nuclear energy.
The countries' declaration followed a speech by Russian President Vladimir Putin calling on the Caspian nations not to let any third country use their territory for an attack, a comment apparently directed at former Soviet state Azerbaijan.
The US military has inspected airfields in Azerbaijan, which has a partnership deal with Nato, and there has been Russian media speculation they could be planning to use the facilities in a possible strike on Iran.
Azeri officials deny any such plan.
Iranian President Mahmoud Ahmadinejad, who insists Tehran will not stop atomic work he insists is peaceful, praised the Caspian declaration as "very strong".
The presence of Mr Putin, the first Kremlin leader to visit Iran since 1943, has been watched because of Russia's potential leverage, on behalf of fellow world powers, to rein in Iran using its trade and nuclear supply ties with Tehran.
"We should not even think of making use of force in this region," Mr Putin told the summit.