By Sadeq Saba
BBC regional analyst
Iran's agreement to meet the key demands of the International Atomic Energy Agency is a major victory for President Mohammad Khatami and his reformist allies.
They have been arguing all along that the country had no realistic choice but to be more co-operative about its nuclear activities.
Khatami is relying on the silence of Iranian hardliners
They can now argue that they have saved the Islamic Republic from possible United Nations sanctions and possible unilateral action by the US.
But the deal will be a bitter pill to swallow for the hardliners who have been saying that Iran should give no concessions and should even pull out of the Nuclear Non-Proliferation treaty.
Iran's supreme leader, Ayatollah Ali Khamenei, has been crucially silent since the IAEA issued its ultimatum against Iran four weeks ago.
But the deal in Tehran would not have been possible without his tacit endorsement.
Nonetheless, Mr Khamenei and his hardline allies face a big difficulty in selling the agreement to their supporters.
But because the hardliners were not directly involved in the negotiations with the European foreign ministers, they always have the option of accusing their reformist rivals of being responsible for a humiliating agreement.