The two leaders posed for photographs after Putin's arrival at 5:30 pm (2130 GMT) Friday, September 26, but did not speak to the press. They later dined together, according to Agence France-Presse (AFP).

Putin spokesman Alexei Gromov told Russian news agency RIA Novosti they discussed the reinforcement of U.S.-Russian cooperation, and touched on a number of international problems to be further discussed Saturday.

After wrapping up their talks Saturday, Bush and Putin will give a joint press conference ahead of Putin's afternoon departure.

The two leaders began their summit while still far apart over Russian nuclear ties with Iran, even if Putin's address to the U.N. General Assembly Thursday appeared to soften their differences over Iraq.

Amid mounting Western suspicions of Iran's actions, the United States has been pressing Russia not to sign an accord that would allow Iran's first nuclear power plant - which is being built by Russia - to go live.

According to the BBC online news service Saturday, Bush is expected to call for Russia to suspend nuclear co-operation with the Islamic republic.

Russia has so far turned down American requests to stop helping Iran's nuclear program.

"It is very important for the world to come together to make very clear to Iran that there will be universal condemnation if they continue with their nuclear weapons program," Bush said Thursday.

In Moscow, top Kremlin foreign policy adviser Sergei Prikhodko told Interfax that, from the Russian side, "the purpose of the summit is to speak seriously about what Russia and the United States have achieved, what prevents them from implementing existing understandings, and in what direction they should be working."

Iran Under Renewed Pressure

In a separately-related development, Iran came under renewed pressure Saturday from the U.N. nuclear watchdog, whose chief demanded Tehran for "full and complete cooperation" over its atomic energy program, not just statements of goodwill.

"I hope so, I hope at least that I will not be in a position to report that I am not getting the full cooperation and transparency from Iran.

"There is a degree of impatience on the part of the international community that this issue cannot continue for ever. If not, I am afraid that the issue will escalate beyond the confines of the agency," he added.

Tehran, however, has insisted on sticking to its own calendar.

"We will respond when it will be necessary, before or after the 31st of October," a Foreign Ministry spokesman said Monday.

"The resolution is being examined by the concerned officials and this examination is not yet finished."

Iranian Foreign Minister, Kamal Kharazi, has said that Iran only wants to produce enriched uranium to avoid reliance on supplies of nuclear fuel from Russia.

"It is not our policy to have nuclear weapons because we don't believe it will bring security in Iran," he said in New York this week.

Despite Tehran's obstinacy, ElBaradei refused to be drawn into speculation on what might happen if the matter were referred to the U.N. Security Council, which could slap sanctions on the Islamic republic.

"I hope that the issue will not have to be brought to the Security Council. I hope that Iran will cooperate and take whatever corrective measures needed for us to be able to present a positive report," he said.

"They say their program is for peaceful purposes, and if they really have nothing to hide it is (up) to them to open all their facilities and all their books," he said.

"We need to act fast and with the full force that this issue requires.

"They need to understand this is not an ultimatum ... this is an opportunity to come clean through telling us everything they have done."

Nevertheless, ElBaradei conceded that there were "a lot of worrying signs" that Iran's nuclear activities are not civilian only.