"The election of a hardliner Mahmoud Ahmadinejad as the new Iranian president is out of step with the rest of the region and the currents of freedom and liberty that have been so apparent in Iraq, Afghanistan and Lebanon," State Department spokeswoman Joanne Moore said on Saturday.
"These elections were flawed from their inception by the decision of an unelected few to deny the applications of over a thousand candidates, including all 93 women," she said.
"We will judge the regime by its actions. In light of the way these elections were conducted, however, we remain sceptical of the Iranian regime's intentions."
US officials, including President George Bush and Secretary of State Condoleezza Rice, have repeatedly heaped scorn on Iran's presidential poll in recent days.
"Power is in the hands of an unelected few who have retained power through an electoral process that ignores the basic requirements of democracy," Bush had said in a statement last week.
Meanwhile, in Los Angeles, exiled Iranian opposition leaders said Ahmadinejad's victory would bring Tehran's Islamic government a step closer to collapse.
While the election of the conservative Islamist might bring tough times for Iranians in the short term, they said it will ultimately fuel internal opposition, put external pressure on the government and expose cracks within it.
Exiled Iranians say the Islamic
state is now closer to collapse
Some 400,000 to 600,000 Iranians live in the United States, most of them in California.
They said they were shocked but thrilled at the victory of the Tehran mayor, even though his social and political values and beliefs were diametrically opposed to their own.
"We are really excited, this is a very good thing for the opposition to the Islamic republic," said Roozbeh Farhanipour, an activist of the secular Marzepour Gohar political group and a former Iranian student leader who fled to the United States in 2000.
Farhanipour and other activists, who had called for a boycott of Friday's poll, said the result was a sign of deep discontent with the 26-year-old Islamic government and with outgoing reformist President Mohammad Khatami, who failed to implement major political and social changes.
"Ahmadinejad is a short cut for the opposition and a move toward the revolution. I hope that this is the last president of the Islamic Republic."
While the multiple exiled Iranian opposition groups are deeply divided on many issues, all those reached by AFP agreed that the new Islamist leadership would shorten its lifespan.
"Ahmadinejad is the Islamic Republic at its best," said Bihan Mehr, of the Iran National Front, or Jebhe Melli, a liberal democratic party founded in Iran in 1950 but branded infidel by the Islamic government.
"With this guy, the world and Iran will get to the bottom of the problem real quick," said the 46-year-old property developer, who left Iran when the last shah was toppled in 1979.
Akbar Hashemi Rafsanjani, the man who lost Friday's presidential polls, would have presented a more moderate face to the world, extending the tenure of the Islamic government, Mehr claimed.
Rafsanjani would have shown a
more moderate face to the world
"The voters had a choice between a hardliner and a thief and they chose the right guy for the opposition," Mehr said.
"Now the opposition must organise quickly."
There will be no fooling anyone. I think this has sped up the process of recognising the brutality and lack of skill of this regime," an ecstatic Mehr said.
Indonesian Islamists cheered Ahmadinejad's victory while a Muslim scholar suggested the landslide victory was driven by anti-US sentiment in the Middle East.
"I'm glad and happy to know Iran's election result," said Irfan Awwas, a leader of Majelis Mujahiddin Indonesia, a Islamic group whose founder, Abu Bakr Bashir, is in jail for his alleged role in the deadly 2002 Bali bombings.
"Iran's people think the hardliner candidate is more fit for them compared to Rafsanjani," Awwas said.
"People there might think Rafsanjani is more fit to manage international relations, especially with Western countries, but not to lead the country."
"The people of Iran are to be congratulated for the tremendous support and enthusiasm they have shown for the democratic electoral process"
Foreign Ministry spokesman
Komaruddin Hidayat, an Islamic scholar, said the victory is a reaction to America's ongoing war in Iraq and its invasion of Afghanistan.
"America has put Islam in a corner," Hidayat said.
Indonesia's official response was more muted, with a Foreign Ministry spokesman preferring to focus on the election itself rather than the winner.
"The people of Iran are to be congratulated for the tremendous support and enthusiasm they have shown for the democratic electoral process," Foreign Ministry spokesman Marty Natalegawa said.
"As the task of governance beckons, we are confident that we can continue to rely on Iran as a force for peace, stability and moderation in its own region and beyond," he said.