"The international community is united that there must be a strong message to Iran through the Security Council that their behavior to date is unacceptable," Rice said a day after world powers failed to agree on an approach to Tehran.

Russia and China, which both wield a veto on the Security Council, have opposed coercive measures against Iran for its suspected efforts to develop nuclear weapons.

But Rice told reporters after a Security Council meeting on Darfur here that "the United States believes very strongly in a mandatory statement from the Security Council to Iran."

Chapter seven resolutions can authorize sanctions or even the use of force against Iran, but article 40 of the chapter can give the concerned party time to comply before any action is taken.

Asked whether an article 40 would be sufficient for the United States, Rice said, "I'm not going to get into the diplomacy. Let's give it time to work."

She also appeared unconcerned by the delay in approving a resolution on Iran six weeks after the matter was referred to the Security Council by the International Atomic Energy Agency (IAEA).

"We're going to take the time that we need to make certain that the members of the international community have an opportunity to develop a strategy moving forward," Rice said.