The encounter will cap off an extraordinary, weeks-long attempt by European Union foreign policy chief Javier Solana to convince Iran to suspend its uranium enrichment program as demanded by a UN Security Council resolution.

Solana admitted this week that the effort had failed to sway the Islamic Republic's hardline leaders, who reject claims by the US and others that the enrichment program is aimed at producing fissile material for nuclear bombs.

US Secretary of State Condoleezza Rice said Friday's meeting, which involves the five veto-wielding permanent UN Security Council members plus Germany, would shift the Iran effort from negotiations to punishment.

"What the ministers are going to do... is to say 'We've done the Solana effort, and now we'll have to move to sanctions'," she said during a surprise visit to Baghdad.

Britain's ambassador to the United Nations, Emyr Jones Parry, said earlier Thursday that once the so-called P5-plus-1 ministers give the green light, discussions would begin at the UN next week on a sanctions resolution.

Britain "will be discussing with its partners and with members of the council the basis for action by the council to adopt measures under Article 41 against Iran," he said.

Article 41 of the UN Charter allows the Security Council to impose diplomatic and economic sanctions on member nations to enforce compliance with its resolutions.

But despite the confident statements from the US and Britain, there were no indications either Russia or China, both economic allies of Iran, had backed away from their strong reticence to use sanctions.

The two countries' foreign ministers were the last to confirm their participation in Friday's meeting, a senior diplomatic source here said, holding up a decision to go ahead with the gathering for several hours.

Russian Foreign Minister Sergei Lavrov, on a visit to Warsaw Thursday, still showed little eagerness to move ahead with sanctions.

"We will continue with the diplomatic effort, even though some are in favor of sanctions as of now," he said.

Senior diplomats from the six nations who have been working on an initial package of sanctions to use against Iran will also meet in London Friday to pursue their work, the State Department said.

Washington has been pressing its partners to impose a progressive series of sanctions against Iran since Tehran missed an August 31 deadline set in an earlier Security Council resolution demanding an end to uranium enrichment.

Iran, one of the world's major oil producers, says the enrichment program is to provide fuel for nuclear power plants. The United States and others believe it is to produce fissile material to make nuclear bombs.

Rice agreed at a six-power meeting in New York last month to give Solana until this weekend to convince Iran to comply with the UN resolution in exchange for a package of economic and diplomatic rewards.

Solana on Thursday admitted his efforts had failed so far and that "the time of negotiations of course is not infinite."

Rice has said the US wants a graduated series of sanctions, to be implemented through multiple UN resolutions that would ramp up pressure on Iran if it persists with its nuclear program.

The first set of measures is expected to focus on preventing the supply of materiel and funding for Iran's nuclear or ballistic missile programs.

Other steps could include asset freezes and travel bans on officials linked to Tehran's weapons programs.

Even if China and Russia agree to the first set of sanctions, many analysts say the timid measures being considered would have little immediate impact.

"You can get a peanut of a sanctions resolution passed by the UN, but it won't be strong enough to significantly affect Iran's behavior," said Joseph Cirincione, a non-proliferation expert at the American Center for Progress in Washington.

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