Russia and Iran have signed a nuclear fuel agreement -- despite U.S. objections that Iran is trying to develop nuclear weapons. Russian and Iranian officials signed the deal Sunday at Iran's Bushehr nuclear plant, which Russia helped build. Under the agreement, Moscow will supply fuel for the plant. The spent nuclear fuel will then be returned to Russia to ease concerns that Iran might reprocess it for use in nuclear weapons. U.S. Senator John McCain called the deal a very serious step. He told Fox News Sunday that a nuclear-armed Iran would be very destabilizing. Iran insists its nuclear program is only for generating electricity. The International Atomic Energy Agency board is set to meet Monday in Vienna, and Iran's nuclear program is expected to be on the agenda.