The head of the UN nuclear watchdog said he is hopeful of progress in the standoff over Iran's nuclear program following a cooperation agreement, but cautioned Iran against wasting "a great chance - perhaps the last one," according to an interview released Saturday. Mohamed ElBaradei's International Atomic Energy Agency and Iran agreed last month on a timetable to respond to lingering questions over Teheran's nuclear activities. "There are hopeful, positive signals," ElBaradei was quoted as saying in an interview with the weekly Der Spiegel, released ahead of its publication Sunday. "For the first time, we have agreed with the Iranians on a kind of road map, a timetable according to which the outstanding questions should be cleared up." "By November, at the latest December, we should be able to see whether the Iranians are keeping the promises they gave," he said, according to the report. "If they did not do that, a great chance - perhaps the last one - would be lost for Teheran." The US and some of its allies fear Teheran is using its nuclear program as a cover to develop atomic weapons. Iran denies the charge, saying its program is solely geared toward generating electricity. The UN Security Council has already slapped two sets of sanctions on Iran. Iran has rejected the sanctions as illegal, saying it will not give up its right under the Nuclear Nonproliferation Treaty to enrich uranium. "There are concrete elements of suspicion against Iran - so I am of the opinion that Iran has temporarily forfeited this right and must first win it back through confidence-building measures toward the international community," ElBaradei was quoted as saying. But he said, according to the report, that if the West focuses "only on confrontation, then one can forget dialogue."