Ahead of the meeting, Britain, France and Germany have been canvassing other nations with a two-page summary of the Iranian refusal to honor an August 31 UN Security Council deadline to halt uranium enrichment, the process which makes nuclear reactor fuel but also atom bomb material, diplomats told AFP.

"The summary outlines the conditions Iran is setting for it to join in talks, namely that there is no movement (towards sanctions) against it in the Security Council, and this of course is unacceptable to the West," said a diplomat, who asked not to be named due to the sensitivity of the issue.

In Paris, French Prime Minister Dominique de Villepin told the National Assembly: "Iran's response to the offer made by the international community is insufficient, notably concerning the need to suspend enrichment."

The Berlin meeting is the first reunion of the five permanent UN Security Council members Britain, China, France, Russia and the United States, plus Germany, since Iran defied the Security Council deadline.

The six are offering Iran talks on a package of trade, security and technology benefits if it freezes enrichment.

Discussing ambiguities

In another development, Iran's chief nuclear negotiator Ali Larijani said Thursday in Spain that he plans to meet EU foreign policy chief Javier Solana within days to discuss what he said were "ambiguities" in the benefits offer.

Ali Asghar Soltanieh, the Iranian ambassador in Vienna to the UN nuclear watchdog agency there, told AFP that the Larijani-Solana meeting would be in the Austrian capital, after having been postponed there Wednesday.

In Tehran, a national security council official said that Larijani wants to have "serious and constructive negotiations with the 5 plus 1 group ... especially on the nuclear question."

In Berlin, "they're going to talk about sanctions, and my guess is that they're going to come up with not very much," Chicago-based non-proliferation expert Gary Samore said about the meeting of the six nations' foreign ministry political directors.

No decision-making

A Western diplomat said the gathering was "not a decision-making meeting. It is the first conversation on where we go from here."

Washington leads international concerns that Iran is covertly trying to develop nuclear weapons, something Tehran denies, and the US is also spearheading the push for sanctions.

But Russia and China, both Iranian allies and major trading partners, are reluctant to take such measures, fearing they will worsen the current confrontation or even lead to war.

Mounting impatience

In a sign of mounting international impatience, Russian Foreign Minister Sergei Lavrov said Wednesday Russia was considering support for Security Council economic sanctions against Iran.

"We will consider this from all points of view, in totality, based on our goal of not allowing the spread of WMD (weapons of mass destruction) and technology that is linked with this," state-run RIA Novosti quoted him as saying.

Lavrov said however that Russia still had reservations about imposing sanctions on Iran and he underlined Moscow's opposition to military action.

Robert Joseph, US under secretary of state for arms control and international security, said he believed a vote on sanctions could come this month, and he expected Russia and China would sign on.

The campaign picked up pace after President George W. Bush on Tuesday branded Iran's leaders "tyrants" and said they must not be allowed to get nuclear weapons, "the tools of mass murder."

Iranian President Mahmoud Ahmadinejad hit back saying Bush was "nothing" compared to God's will.