The US and France say they will push for new UN anti nuclear sanctions against Iran, after the Middle East state revealed it was going to step up its uranium enrichment.
Iran's move to boost its enrichment capacity again surprised Western nations who fear that the Islamic republic is trying to develop its own nuclear weapon.
Australian Foreign Minister Stephen Smith said Iran's move was a "serious provocation" that would constitute a clear breach of UN resolutions.
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French President Nicolas Sarkozy and US Defence Secretary Robert Gates agreed in talks on Monday that tough new sanctions must be passed against Iran, the French presidency said.
'Strong' sanctions ahead
Sarkozy and Gates "agreed that the time has come for the adoption of strong sanctions, in the hope that dialogue will be resumed", an official at the French presidency said after a meeting between the two leaders.
French Defence Minister Herve Morin, speaking after earlier talks with Gates, said: "We have no choice but to work on other measures."
Gates said: "We have to face the reality that if Iran continues and develops nuclear weapons, it almost certainly will provoke nuclear proliferation in the Middle East. This is a huge danger."
Tensions have been heightened by Iran's announcement to the International Atomic Energy Agency (IAEA) that it would start enriching uranium to 20 percent from Tuesday.
The IAEA, backed by the international powers, had proposed a deal which envisages 3.5 per cent uranium being sent to Russia and France for enrichment to 20 percent and then returned as fuel for a research reactor in Iran. A nuclear weapon would require enrichment to 90 per cent.
Iran's announcement came less than a week after it signalled support for the UN-drafted deal.
Concerns mount over Iran's plans
IAEA director general Yukiya Amano was worried about Iran's decision to begin higher enrichment, a spokeswoman said.
"Amano noted with concern this decision, as it may affect, in particular, ongoing international efforts to ensure the availability of nuclear fuel for the Tehran research reactor," said Gill Tudor.
"The director general reiterated the agency's readiness to play an intermediary role," she added.
Germany said Iran's announcement showed it was not co-operating with the international community. Britain's Foreign Office said Iran's "contradictory rhetoric" was "deeply worrying".
'A step backward'
A top Russian lawmaker called it "a sure step backward" and suggested new sanctions should be discussed -- a step Moscow has previously opposed.
"The international community should ... send Tehran a new message about its intention to react with serious measures -- to the point of tougher economic sanctions," said Konstantin Kosachev, who heads the Russian parliament foreign affairs committee.
Russia's foreign ministry said Iran must send its uranium abroad as a way out of the impasse, Interfax news agency reported.
Nevertheless, French Foreign Minister Bernard Kouchner warned that it may take time to secure a new UN sanctions resolution.
