Australia said Thursday it has blocked three shipments to Iran under anti-nuclear proliferation laws as the United States and its allies stepped up calls for new sanctions against the Islamic state.

Amid criticism of rocket launch by Iran, countries that fear it is trying to develop a nuclear bomb also called on the Teheran to follow up on comments by President Mahmoud Ahmadinejad that he is ready to agree a uranium enrichment deal that could ease proliferation concerns.

Australian Prime Minister Kevin Rudd said his country had blocked three shipments of unidentified cargo to Iran invoking a rarely used Weapons of Mass Destruction Act.

The prime minister did not give details of the cargo. But The Australian newspaper reported that at least one of the orders made in recent months blocked a shipment of pumps which could have been used to cool nuclear power plants.

"If you look at the threat to regional and global peace which Iran poses in its current nuclear weapons program, there is no alternative other than robust international action including in areas such as this," Rudd told Australian broadcaster ABC.

The United States and France led condemnations of Iran for launching its Kavoshgar 3 (Explorer) rocket -- which Iran said carried a capsule containing a rat, turtle and worms and was an experiment in sending living creatures into space.

The US White House called the launch "provocative".

France believes "this announcement can only reinforce the concerns of the international community as Iran in parallel develops a nuclear programme that has no identifiable civil aims," a foreign ministry spokesman said.

Iran strongly denies it is trying to develop a nuclear bomb, but US Defense Secretary Robert Gates told a Congress committee that Iran faces the prospect of "severe sanctions" over its atomic activities.

"I think in the near term it's more likely to be severe sanctions imposed partly by the UN Security Council and partly by the United States and like-minded countries," Gates said when asked about a warning to Iran made by President Barack Obama.

The UN Security Council has already passed three rounds of sanctions against Iran and the six nations seeking to limit Iran's nuclear programme are to meet soon to discuss new measures.

A fierce international debate is likely as China and Russia, permanent members of the Security Council, have traditionally opposed action by the United States, France, Britain, Germany to impose tough measures.

Chinese Foreign Minister Yang Jiechi warned that threatening sanctions will derail diplomatic efforts to resolve the Iran nuclear dispute.

"This talk of sanctions at this moment will complicate the situation and stand in the way of finding a diplomatic solution," Yang told a gathering at a French think-tank in Paris.

Iran's president surprised the West on Tuesday by suggesting that a deal under which Iran would send low-enriched uranium abroad was suddenly back on.

The western alliance urged Iran to quickly follow up the comments by signalling its agreement to the International Atomic Energy Agency (IAEA), the UN watchdog that brokered the deal.

"If those comments indicate some sort of change in position for Iran, then President Ahmadinejad should let the IAEA know," said deputy White House spokesman Bill Burton.

Iran needs nuclear fuel to power a UN-monitored research reactor, but the West fears its uranium enrichment program is masking efforts to produce atomic weapons -- claims vehemently denied by the Islamic republic.

The IAEA has proposed that Tehran ship out its low-enriched uranium to Russia and France to be further purified into reactor fuel.

The Islamic Republic, which agreed in principle to the offer during talks with world powers in Geneva in October, later appeared to reject the deal and said it preferred a gradual swap of uranium for fuel -- preferably on Iranian soil.

Britain's Foreign Office said Iran should make "clear" to the IAEA any willingness to take up the proposal.

"Iran has to make concrete commitments to the IAEA and a concrete answer in Vienna is the only measure on which it can be assessed," German government spokesman Ulrich Wilhelm said.

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