A top Iranian envoy defiantly rejected a U.N. Security Council demand for a halt in uranium enrichment, saying Thursday that Tehran's activities are "not reversible," despite new calls to reconsider from the Security Council. 

U.S. Secretary of State Condoleezza Rice answers questions during a news conference with her counterparts in Berlin on Thursday, March 30, 2006, after a meeting with Foreign Ministers from Russia, China, Germany, Britain and France to focus on ways of detering Iran from pushing ahead with uranium enrichment. [AP]

Ali Asghar Soltanieh, Tehran's chief representative to the International Atomic Energy Agency, the U.N. nuclear watchdog, said "it is impossible to go back to suspension.

"This enrichment matter is not reversible," he said in a telephone call from Vienna, Austria.

Iran's defiance cast a pall on a meeting of top officials of the five permanent Security Council members plus Germany meant to demonstrate consensus on confronting Tehran over its nuclear program. After two hours of talks that were twice as long as planned, Secretary of State Condoleezza Rice said the six nations were "united."

But Russia and China suggested otherwise, expressing opposition to strong council action against Tehran after the meeting in comments that reflected the continuing fault-line dividing East and West on Iran.

Russian Foreign Minister Sergey Lavrov specifically challenged U.S. assertions that Iran was trying to make nuclear arms, saying no proof existed of such claims.

While symbolizing unity after weeks of tenuous negotiations led to Wednesday's watered-down Security Council statement, a European official who was briefed on the closed talks told The Associated Press that the meeting did not bridge differences that left Russia and China at odds with the United States, France and Britain.

Russia and China remained opposed to the next step called for by Washington, Paris and London ¡ª a strong resolution that is legally binding and, at least in theory, is enforceable by military means, according to the official, who spoke on condition of anonymity because he was not authorized to talk about the closed meeting.

That stance left the Western powers at the Berlin talks unwilling to consider any specific suggestions on a "parallel track" favored by Russia to Security Council action ¡ª multilateral negotiations with Iran, including some or all permanent council members and Germany, the official said.

But a U.S. official told the AP that if talks with Iran on Iraq were fruitful, they could be expanded to touch on the nuclear issue.

The Bush administration and Iran have publicly emphasized those talks would focus on Iraq. But the official, who spoke on condition of anonymity because he was not authorized to talk to the media, said that "if some understanding emerges from those discussions, then the one side or the other might say, 'Let's have some follow-up.'"

The meeting of the foreign ministers, along with a senior Chinese official and Javier Solana, the top EU foreign policy official, came a day after the Security Council agreed on a statement calling on Iran to reimpose its enrichment freeze and cooperate with an IAEA inquiry.

It asked IAEA head Mohamed ElBaradei to report in 30 days on whether those requests were made. But the statement was stripped of tougher language backed by the West in deference to Russia and China.

Iran has used the weeks of wrangling within the council to make progress on its enrichment program ¡ª which can be used both to generate fuel or make the core of nuclear weapons. Diplomats familiar with the IAEA investigation say it is close to introducing uranium gas into 164 centrifuges ¡ª a test facility that nonetheless would give Iran valuable expertise as it works to develop a full-scale enrichment program.

Warning Iran that the international community is united, both Rice and British Foreign Secretary Jack Straw hinted at escalating Security Council action should Iran disregard the demand that it reimpose a freeze on its uranium enrichment program.

German Foreign Minister Frank-Walter Steinmeier held out hope that Tehran might reconsider, despite the Vienna envoy's statement. "We hope that the declaration by the Iranian ambassador is not the last word offered on this," he said.

Steinmeier said the 30-day time limit gives Iran time to "make a choice between isolation ... or a return to the negotiating table."

"We all very much hope that Iran will seize the offer to resume negotiations and we use this opportunity to once again call on Iran to suspend all enrichment activities and to open up once again the path leading to negotiations," he said.

In Geneva, Iranian Foreign Minister Manoucher Mottaki avoided specifics on the enrichment issue, but appeared to rule out any hope of a negotiated resolution.

"Three years of negotiations have just added to our mistrust," he told the 65-nation Conference on Disarmament, alluding to failed talks with France, Britain and Germany focusing on trying to persuade Tehran to give up enrichment out of fears it would be misused to make nuclear arms. He said there is "no prospect of final agreement."

Seizing on the unity theme touched on by Rice and others, Straw said the Iranians "have miscalculated" in hoping to divide the international community. Instead, he said, "they have become more and more united."

French Foreign Minister Philippe Douste-Blazy said all present agreed the council could "use its political" power to enforce demands on Iran.

Still, comments by Lavrov, and Dai Bingguo, a deputy Chinese foreign minister, revealed that opposition by Moscow and Beijing persists to robust Security Council action, as sought by Washington, Paris and London.

"Russia on principle doesn't think sanctions can achieve a settlement" that would lead Iran to compromise on enrichment and other demands backed by the Security Council, Lavrov said.

"Before we call any situation a threat, we need facts ... (and) so far they have not been provided," he said, arguing that there is no evidence that Iran is hiding a nuclear weapons program ¡ª as asserted by Washington.

Lavrov's call for moderation was echoed by Dai, who called for a "peaceful solution" and added there was "too much turmoil" in the region.

"This issue is among the most difficult and complicated in today's world, it requires time, persistence and wisdom, and it can only be resolved through peaceful means," he said.