Deputy Foreign Minister Georgy Mamedov called on Tehran to provide international guarantees that its energy program has only peaceful aims. In a meeting with Iranian Ambassador Gholamreza Shafei, Mamedov expressed concern about the existence of "serious, unresolved questions in connection with Iran's nuclear research."
Mamedov said Iran should sign "as soon as possible" an additional agreement with the IAEA to put all of Tehran's nuclear facilities under closer scrutiny.
The Bush administration has accused Iran of secretly embarking on a program to enrich uranium at Natanz in southern Iran, which American officials fear could be used to make nuclear weapons.
Washington wants the International Atomic Energy Agency to declare that Iran has violated the nuclear Nonproliferation Treaty when the U.N. nuclear watchdog agency meets next month.
The opposition National Council of Resistance of Iran (NCRI) has been tracking Iran's nuclear development activities though its sources inside Iran.
The administration confirmed an NCRI report last August of a uranium enrichment facility and is now examining a new NCRI claim of two additional enrichment facilities 40 miles west of Tehran. An NCRI spokeswoman said Tuesday Iran could have a nuclear weapon by 2005.
The National Council is linked to an Iraq-based group that opposes the Iranian leadership, the People's Mujahedeen. Despite being listed as a foreign terrorist organization, after it occupied Iraq the U.S. briefly allowed the group to keep its weapons.
Iran's alleged nuclear program has been one of the major sources of discord between Moscow and Washington, which has urged the Kremlin to curtail its nuclear cooperation with Tehran.
Russia signed a deal with Iran to build a nuclear reactor in the southern city of Bushehr in 1995, shrugging off U.S. concerns that it could help Tehran build an atomic bomb.
Moscow has been trying to mend ties with Washington damaged over the war in Iraq, and has been particularly eager to get the relationship back on track ahead of this weekend's U.S.-Russia presidential summit.
Russian Foreign Minister Igor Ivanov warned Wednesday that Russia won't tolerate criticism leveled against it.
"There are no grounds for complaints directed at Russia," Ivanov was quoted by the Interfax Military News Agency as saying. "There is no point in making unsubstantiated accusations, particularly in the form of an ultimatum."
Iran's alleged nuclear development is only one of several points of contention between Tehran and Washington.
Others include Iran's alleged harboring of al Qaeda operatives linked to the May 12 bombings in Saudi Arabia and Tehran's alleged attempts to influence events in postwar Iraq.
The White House on Tuesday postponed a meeting to discuss a possible new strategy on Iran — a session which, according to published reports, was to consider support for a new policy of regime change there.
Secretary of State Colin Powell denied that a new approach was under consideration.
"Our policies with respect to Iran have not changed," Powell said Tuesday. "We do not approve of their support of terrorist activities. We have made it clear over the years that we disapprove of their efforts to develop a nuclear capability."
Powell said contacts with Iran continued. But the U.S. cancelled the latest scheduled meeting, and in recent weeks administration officials — including Powell — have strengthened their rhetoric towards Tehran.
In remarks Tuesday, Defense Secretary Donald Rumsfeld again warned Iran to stay out of affairs in neighboring Iraq. The United States suspects Iran of meddling in Iraq through anti-Saddam Shiite groups it supports.
"Iran should be on notice that attempts to remake Iraq in Iran's image will be aggressively put down," he said.
For his part, Iran's President Mohammad Khatami opened a meeting of the foreign ministers of Muslim-majority countries today with a call for power to be placed in the hands of Iraqis "as soon as possible."
In reply to a question, Rumsfeld said the administration was debating the most effective way to deal with Iran — through the hard-liners in charge, through the moderate leaders they tolerate or directly with the Iranian people.
The U.S. says five suspected al Qaeda members allegedly sheltering in Iran may be linked to the May 12 bombings in Riyadh, which killed 34 people, including eight Americans. The White House said Tuesday that the arrests Iran claims to have made of al Qaeda members were not enough.
"The steps that the Iranians claim to have taken in terms of capturing al Qaeda are insufficient," spokesman Ari Fleischer said. "It is important that Iran live up to its commitments and obligations not to harbor terrorists."
The U.S. has said Iran must not only arrest al Qaeda members but also hand them over to Saudi Arabia.
However, Fleischer said, "it's a diplomatic course that the president is pursuing" with respect to Iran.
A turning point in that approach could come next month when the IAEA visits Iran to inspect the country's nuclear facilities. A finding that Iran is in violation of its Nuclear Non-Proliferation Treaty commitments could put the issue before the U.N. Security Council.