Iran says it could end all voluntary cooperation with the United Nations nuclear agency if the agency refers Tehran to the U.N. Security Council for possible sanctions over its nuclear program. All sides are now talking about the nuclear standoff in stark terms, and appearing to rule out compromise.

Iran's Foreign Minister Manouchehr Mottaki says a recently passed law gives Tehran no choice but to end cooperation with the International Atomic Energy Agency if its nuclear program is referred to the Security Council.

On Thursday, the British, French and German foreign ministers said Tehran's decision to resume uranium enrichment leaves them with no choice, either. Their statements were echoed by Secretary of State Condoleezza Rice.

Condoleezza Rice

"We agree that the Iranian regime's defiant resumption of uranium enrichment work leaves the EU with no choice but to request an emergency meeting of the IAEA board of governors," she said. "That meeting would be to report Iran's non-compliance with its safeguards obligations to the UN Security Council."

Iran's traditional ally, Russia, has said it will not block the referral of the matter to the Security Council, but it is trying to tone down the discussion.