The U.S. has offered to provide Iran with medical isotopes to treat cancer patients in desperate need, which had been Tehran's rationale for enriching uranium. The offer, made with other countries and to be presented to the International Atomic Energy Agency, is an attempt to call Iran's bluff. The U.S. believes Iran's motives are not to aid sick people but to build up its nuclear-weapons capabilities. A state department spokesperson said the plan would be the "safest and cheapest" way for Iran to acquire the medical isotopes and could "build confidence" with western nations, which are pushing for sanctions against Iran for its nuclear activity. Iran maintains its nuke program is peaceful.