The United States may turn to the U.N. nuclear watchdog agency to exert more pressure on Iran out of frustration with Russian and Chinese opposition to firm Security Council action, diplomats said Wednesday.

The diplomats told The Associated Press that the U.S. delegation to the International Atomic Energy Agency has contacted other nations over the past few days to gauge support for a special IAEA board meeting on Iran's nuclear program.

But the envoys — who were familiar with talks on Iran's nuclear dossier but spoke on condition of anonymity because they were not authorized to reveal the American initiative — emphasized that no decisions had been made on the idea.

Still, the fact that Washington was contemplating such action was significant.

U.S. officials have for weeks been publicly in favor of shifting international attention over Iran's nuclear program from the Vienna-based agency — which has no enforcement authority — to the Security Council, which has the power to impose sanctions backed by the threat of military force.

Years of U.S. lobbying paid off in February, when the IAEA's 35-nation board agreed to refer Iran's nuclear file to the more powerful U.N. body. But since then, the council's five veto-packing members have been divided, with Moscow and Beijing opposing efforts by the U.S., France and Britain to move from requesting Iranian compliance to demanding it.

The split appeared to persist Wednesday.

Russian Foreign Minister Sergey Lavrov urged Iran to halt all uranium enrichment after a meeting in Moscow among senior officials of the five permanent council members plus Germany, but he acknowledged the talks produced no decision on how to proceed if Tehran fails to comply.

U.S. Undersecretary of State Nicholas Burns told the AP in Moscow that the possibility of sanctions had been discussed but indicated more talks were needed.

"What is new is a greater sense of urgency given what the Iranians did last week," Burns said later to reporters, alluding to Iran's announcement that it had succeeded in enriching uranium.

Burns, echoing a statement Tuesday by President Bush, did not reject the possibility of a military response.

"Obviously, the United States always keeps all options on the table ... but we're focused on diplomacy," he said.

In Paris, French President Jacques Chirac and Egyptian President Hosni Mubarak said they were opposed to military intervention in Iran.

"We have to explore all the possibilities offered by a diplomatic option in order to avoid a destabilization of the Middle East, and probably of the rest of the world," Chirac said at their joint news conference.

Military strikes against Iran "would have very grave effects" on the region, Mubarak said.

Lavrov said no decisions had been expected at Tuesday's meeting because the nations were waiting for a report this month from IAEA chief Mohamed ElBaradei on Iran's nuclear program. He said Russia wants the report to be reviewed by the IAEA board before it goes to the Security Council, which has set an April 28 deadline for Tehran to suspend enrichment, which can be used to generate power or make the fissile core of nuclear weapons.

Iran says its program is peaceful, but the Americans and dozens of other countries fear it wants the technology to make the core of nuclear warheads.

Russia, which has close economic ties to Iran and is not eager for a discussion of sanctions in the Security Council, repeatedly has stressed that the IAEA is the best forum for discussions on the Iranian program.

That stance has been opposed by the Americans, French and British. But one of the Vienna-based diplomats said Washington appeared to be ready to "fill the gap" by seeking a special board session to bridge over anticipated future weeks of council inactivity.

He said members of the U.S. mission to the IAEA have worked out different scenarios for what such a board meeting could accomplish but refused to go into details. He said the British were opposed because it would complicate the process, "but if the Americans want it, it's going to happen."

U.S. officials in Vienna declined to comment.

The enrichment issue has gained urgency because of recent claims by Iran that — if true — would bring it closer to bomb-making capacity.

Iranian President Mahmoud Ahmadinejad said a week ago that the Islamic republic was testing a sophisticated centrifuge to enrich uranium — something Tehran has denied for years. A day earlier, he had trumpeted Iran's success in enriching a small amount of uranium using a 164 less-sophisticated centrifuges.

Neither claim has been publicly confirmed by the IAEA. Iran would need at least 1,000 of the less advanced P-1 centrifuges working for over a year to produce enough nuclear material for a bomb. Two diplomats, speaking separately, said the IAEA planned to send in two teams of investigators this week to follow up on both claims ahead of ElBaradei's report.