The United States is warning Iran against pursuing new nuclear fuel research, suggesting that such action could lead to international sanctions. Iran told the United Nations nuclear watchdog agency Tuesday it was resuming the research after a pause of more than two years.
The Bush administration says Iran's insistence that its nuclear program is peaceful no longer has any credibility.
And it says if Tehran resumes activity related to uranium enrichment, the international community will have to respond.
The U.S. warning, an implicit reference to U.N. Security Council action, followed an Iranian announcement Tuesday that it would resume nuclear research and development suspended more than two years ago under an agreement with Britain, France and Germany.
Iran's atomic energy agency was not specific about the activities to be restarted, but said the work would not be related to nuclear fuel production.
However European officials said the Iranian announcement, following an August decision to resume uranium conversion, was a further blow to diplomatic efforts to resolve the crisis over the Iranian program.
At a news briefing, State Department Spokesman Sean McCormack said Iranian evasiveness and failure to cooperate with the International Atomic Energy Agency has broken down any sort of trust that may have existed between Tehran and the world community.
Reiterating the U.S. stand that Iran is seeking nuclear weapons, he said renewed action on enrichment should bring an international response.
"If Iran takes any further enrichment-related steps, the international community will have to consider additional measures to constrain Iran's nuclear ambitions," he said. "And I think that Iran should listen very carefully to the international community. It finds itself increasingly isolated on this issue."
The Bush administration has long held that the issue of the Iranian nuclear program should be referred to the U.N. Security Council for possible sanctions, but has nonetheless supported the European initiative to resolve the issue short of referral.
Mr. McCormack said that as a country rich in oil and gas, Iran's stated insistence that it needs a civilian nuclear power capacity is frankly inexplicable.
He said the international community has gone more than the extra mile in trying to address Iran's concerns about access to nuclear fuel, but that Tehran has only pocketed those proposals and offered nothing in response.
The overture by the so-called EU-Three aims to wean Iran off its suspected nuclear ambitions with a package of economic and security initiatives.
Russia has put forward an offer to enrich fuel on its territory for Iran's nearly completed Bushehr nuclear plant and other planned facilities, and to re-claim spent fuel from Iran afterwards.
Spokesman McCormack sidestepped a question about whether Iran might just be buying time to pursue its nuclear aims, but said Tehran is certainly not engaging in good-faith negotiations.