In a concerted effort, US Undersecretary of State Nicholas Burns was due to meet with top European diplomats in London Saturday.

In Ottawa Friday, US Secretary of State Condoleezza Rice expressed hope that Russia would support a second Security Council resolution for sanctions against Iran to force an end to its nuclear programme, after talks with her Russian counterpart a day earlier.

The United States, France and Britain have called for tougher Security Council sanctions on Tehran, while Germany, China and Russia have taken softer stances.

"It would be a serious mistake if a nation like Iran were to become a nuclear power," Cheney warned during a joint press conference with Australian Prime Minister John Howard. "All options are still on the table."

The International Atomic Energy Agency (IAEA) has issued a report saying that Iran had not halted, and in fact had expanded, its uranium enrichment programme, defying a UN Security Council demand to stop by this week.

"We've worked with the European Community and through the United Nations to put in place a set of policies to persuade the Iranians to give up their aspirations," said Cheney. "That's still our preference."

"The next step now is being debated, between our government and the others involved," he added.

"Nick Burns, the number-three man at the (US) State Department, is in London today to negotiate with our European friends... on the future course of action we want to pursue with respect to the United Nations sanctions and so forth," he said.

Rice Friday downplayed the likelihood of US military action against Iran.

"I don't want to speak for my Russian colleague, but... we would expect to continue to pursue our Security Council track as well as to pursue a track that would hopefully lead to negotiations," Rice said during her visit to Canada.

"I expect on that, we're all on the same page," she said.

Rice met with Russian Foreign Minister Sergei Lavrov in Berlin on Thursday.

"Our envoys... will meet in London next week to examine the prospects for a Security Council resolution," Rice said.

"I believe that everybody understands the importance of continuing to show the Iranians that there is both a Security Council track if they will not adhere to international standards and a negotiated track if they will."

Asked if military action to force Iran to abandon its nuclear ambitions was imminent, Rice said: "We've been very clear that we're on a diplomatic path, that we believe the diplomatic path can succeed if the international community stays unified in confronting Iran with the consequences of its continued defiance of the international community."

"It is the international community, not the United States. It's the international community on a vote of 15-0 in the Security Council that has said that Iran must suspend its enrichment and reprocessing activities.

"And so we are joined with the international community in showing Iran that this activity, this path that they're on, is one of isolation, but that there's another path.

"We have, with our partners in the European Union, Russia and China, put forward a proposal for widespread economic and political cooperation with Iran through a negotiated process, and we continue to hope that Iran will take that path rather than the one of confrontation."

Iran says it cannot accept UN demands that it halt enrichment of uranium, because they are contrary to its rights under the nuclear Non-Proliferation Treaty.

While many nations suspect weapons ambitions, Iran insists the research is to produce civilian energy. Uranium enrichment is a key stage of making a bomb and energy production.

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