The United States and Iran clashed at the United Nations on Monday over Tehran's nuclear program and its selection to be one of dozens of vice presidents at a monthlong conference to review the Nuclear Non-Proliferation Treaty.

The 11th conference to ?review the implementation of the NPT, which came into force in 1970, began on Monday ?at ?the United Nations in New York. Different groups nominated 34 conference vice presidents, ?and the conference chair, Vietnam's U.N. ambassador Do Hung Viet, said Iran was picked by "the group of nonaligned and other states."

Christopher Yeaw, assistant secretary for the U.S. Bureau ?of Arms Control and Nonproliferation, told the conference that Iran's selection was an "affront" to the NPT.