Speaking at the IAEA meeting of the Board of Governors, U.S. Ambassador George Shulte said, "Iran's refusal to suspend and its refusal to cooperate is a choice of confrontation."

Shulte said that such a position would result in further isolation and sanctions.

The U.S. official said that "we must take further steps to persuade Iran to abandon its nuclear weapons ambitions."

"Iran must abandon its quest of nuclear weapons and fully meet its nonproliferation obligations," Shulte said, adding that the United States has worked with Europe, Russia, China and other like-minded countries to present Iran's leaders with a clear choice.

The negative choice is for Iran to maintain its present course of defiance -- violating the mandatory conditions laid out by the international community, while the positive choice is for it to cooperate and take tangible steps to assure the international community that their nuclear program is peaceful, Shulte said.