Top foreign ministry officials from the five veto-wielding UN Security Council members -- Britain, China, France, Russia and the United States -- plus Germany headed into the talks at around 1800 GMT.

After the meeting at the French foreign ministry, also attended by a representative of European Union policy chief Javier Solana, the envoys were to continue on to dinner.

World powers are trying to reach agreement over what economic sanctions to impose on Iran for ignoring a UN deadline of August 31 to stop enriching uranium -- which outside powers fear could be used to make nuclear weapons.

French Foreign Minister Philippe Douste-Blazy -- who earlier said the meeting had a strong chance of succeeding -- was more reserved in comments to the press Tuesday evening in Paris.

"I don't know if we will have an agreement tonight. We will have to wait and see," Douste-Blazy said.

"I hope we reach an agreement. The unity of the international community depends on the efficiency of this resolution," he added.

US Undersecretary of State for Political Affairs Nicholas Burns also warned reporters Tuesday in Brussels he was not expecting a "breakthrough" in Paris but that it would be "an important meeting".

"We really need the Russian and Chinese governments to move into third or fourth gear.... This afternoon (in Paris) would be a good start."

Moscow and Beijing -- who have strong economic interests in Iran -- have tried to water down a draft UN Security Council resolution put together by Britain, France and Germany, while Washington wants to beef the text up.

The European draft would bar trade with Iran in goods related to its nuclear and ballistic missile programs and slap financial and travel restrictions on persons and agencies involved.

Russian Foreign Minister Sergei Lavrov said Tuesday that Moscow would support a ban on shipments of sensitive goods -- but warned that broader sanctions would be counter-productive.

"We believe it is necessary to approve the proposal on forbidding deliveries of technology, material and services in the field of uranium enrichment, chemical processing of radioactive fuel, and heavy-water technology to Iran from abroad," he was quoted as saying by Ria Novosti news agency.

But he criticised "our Western partners" for supporting the adoption of wide-reaching sanctions that are "not proportionate" to the monitoring capacity of the International Atomic Energy Agency.

"Such a wholesale approach to banning cooperation with Iran in various spheres will only exacerbate the situation," he said.

In Tehran meanwhile, President Mahmoud Ahmadinejad warned Europe that international action over Iran's nuclear programme could endanger relations with Tehran.

"If you (Europeans) continue making efforts to halt the progress of the Iranian nuclear programme and if you take any step against the Iranian nation's rights, either in propaganda or international bodies, the Islamic republic will consider this an act of hostility," Ahmadinejad said in a speech.

"And if you continue with this, the Iranian nation will revise the direction of its path and its plans related to you," he said.

The six powers suspect Iran of trying to develop nuclear weapons under cover of a civilian power generation programme -- which Tehran strongly denies.

On Sunday, Israel approved the creation of a new ministry for strategic affairs, mainly to deal with Iran's nuclear ambitions.

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