VIENNA -- Iran sought yesterday to partially roll back its commitment to freeze all uranium enrichment programs, demanding the right to run some equipment that can be used to produce nuclear arms.
Iran's push to operate 24 centrifuges for what it said were research purposes did not seem to represent a major move, because thousands of centrifuges must operate for months to produce enough enriched uranium for a nuclear warhead.
Still, coming on the eve of a key meeting of the UN nuclear watchdog agency, the demand was likely to strengthen perceptions that Iran's government is not interested in easing fears it is trying to develop atomic arms in violation of the Nuclear Nonproliferation Treaty.
Britain, which helped negotiate the enrichment suspension on behalf of the European Union, rejected the demand. A British official, speaking on condition of anonymity, said the Nov. 7 agreement would stand.
Citing the official EU stance, an EU diplomat accredited to the Vienna-based International Atomic Energy Agency said all centrifuge activity had to remain stopped under the agreement.
The deal committed Iran to full suspension of enrichment and all related activities while the two sides discuss a pact meant to provide Iran with EU technical and economic aid and other concessions.
Iran announced Monday that it had ceased enrichment, while repeating its position that the enrichment program is intended only to produce fuel for generating electricity. Iran denies it is working on atomic weapons.
The suspension was clearly timed to coincide with a meeting today of the UN agency's 35-nation board and met a key demand of the last board meeting in September. It deprived the United States of arguing that Iran was defying the agency and weakened Washington's attempt to refer the matter to the UN Security Council for possible sanctions against Iran.
US officials accuse Iran of secretly developing nuclear weapons.
''Many nations agree with us. Many nations do not -- they think we are overreacting," Secretary of State Colin L. Powell said Tuesday. But he noted that the EU nations felt concerned enough to pressure Iran into stopping enrichment.
The agency's board will also discuss past secret South Korean experiments in plutonium separation and uranium enrichment.
Diplomats said that South Korea's government probably would be reprimanded, but that any decision on referring it to the Security Council would be deferred until agency investigations were complete.
The South Korean government insists it was unaware of experiments that it says were run by renegade scientists -- a contention questioned by some diplomats accredited to the agency and familiar with South Korea's file.
By seeking to exempt some centrifuges from the freeze it agreed to, Iran seemed to reinforce its stance that suspension would be only temporary. It is not prohibited by the nonproliferation treaty from enriching uranium.
A diplomat said the centrifuges Iran wanted exempted were at the central city of Natanz -- where Iran says it ultimately plans to run 50,000 centrifuges.
Tehran says that facility is meant to meet the fuel requirements of a nuclear reactor for an electricity-generating plant being built with Russian help that is expected to be finished next year.
For now, Iran is far short of that goal, possessing fewer than 1,000 centrifuges -- most bought secretly through the black market network of Pakistani nuclear scientist Abdul Qadeer Khan and the rest made domestically.
But analysts estimate the Iranians are not far from being able to run 1,500 centrifuges, which could process enough enriched uranium for one warhead a year.
The New York Times reported today that the recent nuclear accord that European officials signed with Iran appears to have at least temporarily halted Tehran's uranium enrichment program but leaves Iran free to make plutonium, which can also be used as fuel for nuclear weapons. The issue was set aside during recent negotiations as a concession to getting the more limited suspension deal, according to the Times.