Strong U.S. opposition appeared close to torpedoing a Russian initiative that would leave Iran with a small-scale uranium enrichment program, diplomats said Tuesday as Moscow and Washington struggled to find common ground on what to do about Tehran's nuclear ambitions.

One of the diplomats, who spoke outside a 35-nation IAEA board meeting, said Germany also remained open to the proposal, which would allow the Iranians to run 20 uranium-enriching centrifuges domestically while ceding control of large-scale enrichment to Moscow, on Russian soil.

As the board meeting entered its second day, German representatives were meeting with counterparts from France and Britain — which both back the Americans in opposing the plan — to try to re-establish a common European stance on enrichment, said the diplomats, who demanded anonymity in exchange for divulging confidential information.

A European official in Vienna for the meeting said that ultimately the plan would fail if the Americans opposed it.

The dispute, which surfaced in the last few days, was driving a wedge into joint international efforts to wean Iran of all enrichment activity by moving it to Russia, thereby reducing its potential for misuse by Tehran.

The original Russian plan that surfaced last year and is backed by the Americans and the European Union, would have stripped the Iranians of all enrichment potential. But the proposal carried to Washington Monday by Russian Foreign Minister Sergey Lavrov would allow the Iranians a still-to-be-defined "research and development" capacity — including the 20 centrifuges.

The diplomats said IAEA chief Mohamed ElBaradei backed the plan. On Monday, he told reporters a deal on Iran's suspect nuclear program could be only a few days away, making U.N. Security Council action unneeded. Though he did not elaborate, his optimism appeared linked to the Russian proposal on limited enrichment

"I am still very much hopeful that in the next week an agreement could be reached," ElBaradei said.

China's foreign minister also appealed for more negotiations, suggesting no need for Security Council involvement.

"Iran should cooperate closely with the IAEA to settle the nuclear dispute," Li said.

The Americans remained unconvinced. U.S. Undersecretary of State Nicholas Burns said in Washington that "unless Iran does a dramatic about-face," he expected the issue to be taken up by the Security Council.

Later, State Department spokesman Tom Casey said Secretary of State Condoleezza Rice telephoned ElBaradei "to reiterate the U.S. position that Iran should cease all enrichment-related activity." In response, ElBaradei agreed that Iran must not be allowed to have enrichment activity on its territory, said a U.S. official who spoke on condition of anonymity because he was not in position to speak for the IAEA.

There was no official IAEA response. But a diplomat familiar with ElBaradei's stance questioned the U.S. version of ElBaradei's position, saying the IAEA chief remained convinced there was no alternative to allowing Iran some enrichment activity as a way of reaching a deal.

The Russian proposal described by the diplomats would allow Tehran to conduct small-scale uranium enrichment, and would ask the IAEA to set the parameters of such activity to minimize the chances of abuse.

In return, the diplomats said, Iran would be asked to recommit to in-depth IAEA probes of its program on short notice. Iran canceled such investigations last month after the IAEA's 35-nation board put the U.N. Security Council on alert by passing on Iran's nuclear dossier.

France, Britain and Germany broke off negotiations on behalf of the European Union with Iran last year after it resumed enrichment-related activities, which can produce both nuclear fuel and the fissile core of warheads. Since then, they, the United States, Canada, Australia and Japan have been at the forefront of efforts to have the U.N. Security Council take up the Iran issue.

All involved — whether or not they supported allowing Iran some control of enrichment — were firm on the need for Tehran to first return to a freeze of all such activities for a prolonged time "to re-establish confidence," said one of the diplomats

He said the Russians had proposed eight years. A U.S. State Department official, who also insisted on anonymity, refused to specify a length of time but said two years would be too short.

The Vienna meeting is scheduled to hear a report by ElBaradei focusing on Iran's nuclear program, likely on Wednesday.

The last board meeting already had sent the complete Iran file to the Security Council. This meeting is scheduled to pass the ElBaradei report on to the council, which then can decide whether to take action.