But it was still not certain that the meeting, which had already been postponed Wednesday, would go ahead. Neither Brussels nor Tehran has formally confirmed the encounter.

It comes at a time when the United States wants a UN Security Council resolution drafted as early as next week to impose sanctions on Iran over its contested nuclear program, which Washington claims hides secret work to develop the bomb.

This would allow foreign ministers from the six nations trying to win guarantees that Iran will not make nuclear weapons to "complete a sanctions resolution" when they meet in New York at the UN General Assembly the following week, US Undersecretary of State Nicholas Burns said Friday in Berlin.

But Burns told a press event at the American Academy think tank in Berlin that the six nations -- the five permanent Security Council members Britain, China, France, Russia and the United States plus Germany -- "did not come to an agreement" on punitive measures when they met in the German capital on Thursday.

The six are seeking talks with Iran on a package of benefits for the Islamic Republic but demand that Tehran first suspend uranium enrichment, which makes nuclear power reactor fuel but also can produce atom bomb material.

Iran claims it has a right to what it says is strictly peaceful nuclear work to generate electricity. It has defied the six world powers' call for a suspension as well as a Security Council resolution demanding a freeze by August 31 and which threatened sanctions if Tehran did not comply.

Russia and China, which are major trading partners of Iran, are reluctant to impose sanctions, fearing an escalation of the confrontation and possibly even war.

Solana said Friday in Copenhagen that no UN sanctions would be imposed on Iran "as long as meetings with Mr. Larijani continue."

The United States wants clarification of these remarks, which seem to contradict what Burns was saying, the US State Department said Friday.

Solana said it would become clearer on Saturday whether it would be possible to begin negotiations between Tehran and the six world powers.

He said he was "optimistic but not naive" about the outcome of talks with Larijani.

"Saturday's meeting will enable us to see if we can prepare the groundwork" for future talks, Solana said.

"I'm sure that the conversations or discussions will be difficult, otherwise the matter would have been resolved months ago," he said.

"But we have to go into this making every effort in order to succeed," he said.

The touch-and-go Larijani-Solana talks were expected to be held Saturday afternoon in Vienna, diplomats told AFP.

A Vienna-based diplomat said the problem in the two getting together was "because they want to be sure there will be an (good) outcome before they go into the meeting."

"There's a very clear agenda for the meeting", notably to facilitate the resumption of talks, the diplomat said.

Another diplomat said the six world powers were watching how the Larijani-Solana meeting went to see if there was a hope of moving towards negotiations rather than sanctions.

Burns said there would be telephone discussions Monday among the six nations.

"The American view is that following these discussions on Monday and perhaps some others early next week, we should move this to the Security Council and we should draft a resolution," he said.

Burns said the six nations remain committed to their agreement in June to offer Iran benefits but to threaten sanctions if Iran does not halt uranium enrichment.

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