US Secretary of State Hillary Rodham Clinton said Monday that the nuclear offer to Iran, intended to restrain its potential for making a nuclear weapon, should be fully accepted by Iran and will not be changed. "This is a pivotal moment for Iran," she said at a news conference after consulting with senior government officials from several Persian Gulf nations, plus Egypt, Morocco and Jordan. "We continue to press the Iranians to accept fully the proposal that has been made, which they accepted in principle," Clinton said. "Acceptance fully of this proposal ... would be a good indication that Iran does not wish to be isolated and does wish to cooperate with the international community." She said Iran should accept it as it stands, "because we are not altering it." The head of the UN nuclear agency urged Iran on Monday to clarify its response to the proposal that would have Teheran ship most of its nuclear material abroad for processing. The plan is backed by the US, Russia, China, Britain, France and Germany. Iranian officials sent mixed signals on the plan that would have Teheran export 70 percent of its enriched uranium - enough to build a bomb - and have it returned as fuel for its research reactor. The foreign minister said Monday that option still exists; a senior diplomat suggested the opposite. Iran has indicated it wants to purchase higher-enriched uranium from abroad rather than shipping its low-enriched uranium to Russia for further enrichment. The dispute allows Iranian President Mahmoud Ahmadinejad and his hard-line allies to claim the high ground as defenders of Iran's national dignity through its strides in nuclear technology. It also provides Ahmadinejad a chance to broaden support after June's disputed elections, because even his harshest opponents take pride in Iran's nuclear accomplishments.