The United States has accused Iran of seriously escalating the dispute over its nuclear program, after Iran moved to restart nuclear fuel research.
A State Department spokesman, Sean McCormack said Tuesday that U.S. officials were discussing with their allies about how to respond.
European officials also criticized Iran for removing seals at one of its nuclear sites Tuesday. Officials from Britain, France and Germany are to meet this week to discuss referring Iran to the U.N. Security Council for possible sanctions.
The United Nations nuclear agency said Iran announced plans to produce limited amounts of nuclear fuel for research purposes.
But Iranian officials said a suspension on producing nuclear fuel was still in effect.
U.S. and European officials accuse Iran of seeking nuclear weapons -- which Iran denies.