If Iran continues on its current nuclear course, it will leave the international community no choice but to refer Tehran to the UN Security Council for possible actions, the US said today.
EU foreign policy chief Javier Solana
The United States was reacting after Iran removed UN seals at its Natanz uranium enrichment plant and resumed nuclear fuel research.
White House spokesman Scott McClellan warned: "If the regime in Iran continues on the current course and fails to abide by its international obligations there is no other choice but to refer the matter to the Security Council".
If Iran started nuclear enrichment and reprocessing it would be considered a "serious escalation," he said.
Confirming the breaking of the seals, Mohammad Saeedi, deputy head of Iran's Atomic Energy Organisation, said work at the research facilities would resume today under the supervision of the UN nuclear watchdog, the International Atomic Energy Agency (IAEA).
The IAEA confirmed that seals were broken at the Natanz uranium enrichment plant - 49 miles from the historic city of Kashan.
The head of the IAEA, Mohamed ElBaradei, informed his agency's governing board today that Iran intends to begin "small-scale" uranium enrichment work, contradicting previous statements by Tehran.
"Iran plans to install a small-scale gas ultracentrifuge cascade in its pilot fuel enrichment plant at Natanz," a Western diplomat said, reading from Dr ElBaradei's report to the 35-nation board.
Citing the report, the diplomat said that during its research work on centrifuges - machines that purify uranium for use in nuclear power plants or weapons - Iran planned to feed a small amount of uranium hexafluoride into the centrifuges.
The EU was quick to denounce the move. "It is considered a violation of the Paris agreement. These activities are clearly related to enrichment," a spokeswoman for EU foreign policy chief Javier Solana, said.
"This is very much a step in the wrong direction. We are extremely concerned and consultations are taking place to coordinate a response."
Britain also condemned the development and said it put further negotiations with Britain, France and Germany at risk.
However foreign minister Jack Straw said Britain does not envisage military action against Iran either by Britain or by anyone else.
"Military action is not on our agenda, I don't believe in practice it is on anyone else's agenda," Mr Straw told the House of Commons.
Minster for Foreign Affairs Dermot Ahern also criticised Iran's decision to resume nuclear research in defiance of international pressure.
Mr Ahern called on the Middle Eastern country to reconsider the move and call a halt to its nuclear programme.
Mr Ahern said the decision was inconsistent with demands by the IAEA - the world's nuclear energy inspectorate - for Iran to suspend enrichment activities until the international community was confident its nuclear programme was peaceful.
Tehran denies wanting nuclear technology for anything but a civilian energy program aimed at satisfying the Islamic republic's booming demand for electricity.
The United States and the European Union doubt that Iran's atomic ambitions are entirely peaceful.
If the UN Security Council takes up the matter, it could impose economic sanctions.