Russia's President Vladimir Putin has offered qualified support for Iran's nuclear programme on a visit to Tehran.
The historic meeting focused on Iran's nuclear programme
Mr Putin told journalists that "peaceful nuclear activities must be allowed" and cautioned against using force to resolve the dispute over Iran.
But he was evasive when asked whether the Bushehr nuclear plant Russia is building would be finished on time or if Moscow would supply nuclear fuel.
Iran wants Russian help in its dispute with the West over its nuclear aims.
Up to now Moscow has blocked any new UN sanctions, saying it wants to enable the UN's nuclear watchdog, the IAEA, to work with Iran on clearing up outstanding issues.
But Moscow is seeking Iranian compromise over the issue, says the BBC's Jon Leyne in Tehran.
Mr Putin met Iran's President Mahmoud Ahmadinejad for talks after the two men joined the leaders of Azerbaijan, Kazakhstan and Turkmenistan for a summit of the leaders of nations surrounding the Caspian Sea.
Russia is helping to complete Bushehr's nuclear reactor
Heavy security measures were in place amid reports of an alleged plot to kill Mr Putin - reports Mr Putin has shrugged off.
At a news conference, Mr Putin pointed out that the Caspian Sea leaders had signed a declaration which "expressed the idea that peaceful nuclear activities must be allowed".
In the declaration, the leaders also pledged not to allow their territory "for waging aggression or other military action against any of the parties".
Azerbaijan - a US ally - has repeatedly said it would not allow American troops to use its territory to attack neighbouring countries.
Washington has refused to rule out using force against Iran, which it accuses of seeking to acquire nuclear weapons - a charge which Tehran vehemently denies.
Later on Tuesday Mr Putin also held talks with Iran's supreme leader Ayatollah Ali Khamenei.
The Russian president said Moscow had an interest in a "strong Iran" and that he wanted deeper ties with the country, state television reported.
But Mr Putin was evasive about some aspects of Russia's support for Iran.
He refused to confirm whether Moscow would supply the Iranian nuclear plant at Bushehr with nuclear fuel once it is complete, or say whether the plant's construction would be finished speedily.
Mr Putin blamed legal and financial difficulties for the delays that have long dogged the completion of the $1bn building programme undertaken by Russia.
But he said Moscow would not renege on its commitments to complete the plant.
His careful stance suggested Russia is attempting to retain firm ties with Iran without angering the United States, commentators suggest.
It is not clear quite how much support Mr Putin is prepared to give Iran in its showdown with the West.
In 1943 Stalin joined Roosevelt and Churchill for a summit in Tehran
Mr Putin will certainly be calling for more flexibility from the Iranian government over the nuclear issue and no-one should forget the deep legacy of suspicion that exists between Russia and Iran, our correspondent says.
Moscow has urged the international community to show patience in its dealings with Iran.
"It is futile to frighten Iran and its people - they are not scared," Mr Putin said before the visit.
It is the first visit to Tehran by a Kremlin leader since World War II.