Iran's former reformist president declared Sunday that he will run for president again in the country's upcoming elections, posing a serious challenge to hard-line President Mahmoud Ahmadinejad. There had been speculation for months that Mohammed Khatami would seek the presidency in the June 12 vote. The 65-year-old popular reformist is a powerful counterpoint to Ahmadinejad, whose mixture of Western defiance and fiery nationalism sharply contrasts Khatami's tempered tones and appeals for global dialogue. "I seriously announce my candidacy in the next [presidential] election," he announced Sunday during a meeting with his supporters. Khatami said it was impossible for someone like himself who was interested in the fate of Iran to remain silent. He said he decided to run because he was "attached to the country's greatness and the people's right to have control over their own fate." Khatami's landslide presidential victory in 1997 defeated hard-liners who ruled Iran since the 1979 Islamic Revolution. He is credited with relaxing some of Iran's rigid restrictions on cultural and social activities, but he left office in 2005 widely discredited among his political base after hard-line clerics stifled the bulk of his reform program. He had been considered a long shot to return politics after turning his attention to religious and cultural exchanges in recent years. But his candidacy could boost Iran's dispirited reformists, who have not had a political heir emerge since he left office. Hard-liners have vowed they will never again allow reformists to take control of the government and have used the Guardian Council, an election watchdog that vet candidates and the election, and other institutions they control to block reformists from gaining power. It is unclear if the Council will block Khatami's candidacy. The June vote is critical for Ahmadinejad, who was elected in 2005 promising to bring oil revenues to every Iranian family, tackle unemployment and improve living standards, but has increasingly been criticized for his failure to do so. Under Ahmadinejad, Iran has suffered international isolation, skyrocketing prices and disputes over Iran's nuclear program, which the West fears masks a nuclear weapons pursuit. Iran denies the charge. Khatami's decision to run against Ahmadinejad, 52, could significantly shake up Iran's politics, appealing to citizens disillusioned by the country's failing economy and Ahmadinejad's foreign policy. So far, the only other candidate who has announced he is running in the June vote is moderate Iranian cleric Mehdi Karrubi, 71, who is considered a long shot in the race.