White House spokesman Scott McClellan said that Washington is conducting talks with its European allies concerning Iran's nuclear ambitions.
At the U.S. State Department, a spokesman said the issue of Iran's suspected nuclear arms program will likely be referred to the UN Security Council.
British Prime Minister Tony Blair struck the same note today when he said he may seek an international agreement to refer Iran to the Security Council.
German Deputy Foreign Minister Gernot Erler said France, Britain, and Germany cannot continue talks with Iran unless it promises not to begin enriching uranium. He said Iran's removal of UN seals and its announcement that it would resume nuclear research violates an agreement signed by Tehran in 2004.
Under that accord, Iran pledged to freeze all enrichment-related work to ease fears it wants to develop a nuclear bomb.
Iran says its nuclear program is for peaceful purposes only.
The foreign ministers of France, Britain, and Germany and EU foreign policy chief Javier Solana will meet in Berlin tomorrow to discuss the crisis over Iran's nuclear fuel program.