The United States says Iran must stop enriching uranium in order to begin talks on an international proposal to limit its nuclear program.
A State Department spokesman, Sean McCormack says the suspension would have to last throughout negotiations on an incentives package approved by the U.S., Britain, France, Russia, China (the five permanent U.N. Security Council members) and Germany. The spokesman refused to speculate on whether Iran would be able to enrich uranium in the future.
European Union foreign policy chief Javier Solana delivered the package to Iranian officials on Tuesday.
Iran's top nuclear negotiator, Ali Larijani, said the proposal has some positive steps but also contains "ambiguities." He promised Iran will examine it in detail.
Iran's official news agency quotes Iranian Foreign Minister Manouchehr Mottaki as saying Tehran prefers cooperation to confrontation in the standoff over its nuclear program.
Incentives in the package include international support for Tehran's effort to build a power plant running on nuclear energy. The United States would agree to drop trade sanctions, allowing Iran to buy spare parts for its aging fleet of American-made aircraft.
The United States and Europe suspect Iran is trying to develop nuclear weapons -- a charge Tehran denies.