Iran broke U.N. seals at a uranium processing plant on Wednesday, making it fully operational in defiance of the European Union, which urged the U.N. nuclear watchdog to demand that Tehran halt work that could be used to develop atomic weapons.

"The removal of seals has been completed. The plant is fully operational now," Mohammad Saeedi, deputy head of Iran's Atomic Energy Organization, said in Vienna.

Melissa Fleming, spokeswoman for the International Atomic Energy Agency, confirmed that the Iranians had removed all seals on machines at the Isfahan plant in central Iran, although she said they had left some on stockpiled nuclear materials.

The U.N. watchdog put on the seals after Iran agreed, in negotiations with the European Union's biggest powers, to halt all nuclear work after the IAEA found that it had hidden highly enriched, weapons-grade uranium.

Shortly after Iranian officials reopened sensitive areas of the Isfahan plant, Britain, France and Germany submitted a draft resolution to the IAEA's board of governors.

The draft calls on Tehran to immediately resume "full suspension of all enrichment-related activities including the production of feed material," a European diplomat familiar with the text said.

Iran denies accusations that its nuclear program is a front for bombmaking. It says it needs to develop nuclear power as an alternative energy source to meet booming electricity demand and preserve its oil and gas reserves for export.

Under the nuclear Non-Proliferation Treaty, which Iran has signed, it may process and enrich uranium for peaceful purposes. But Britain, France and Germany say the only way for Tehran to prove that its intentions are peaceful is to renounce all sensitive technologies.

Iran restarted work at less sensitive areas of the Isfahan plant on Monday after rejecting economic and political incentives from the three European powers to give up its nuclear program.

State Department spokesman J. Adam Ereli said the breaking of the seals "shows that Iran is just isolating itself further, digging itself deeper into a hole."

He told reporters in Washington that the United States was not immediately calling for Iran to be referred to the U.N. Security Council for possible sanctions because it wanted the Islamic republic to reverse its decision and resume its suspension of sensitive activities.