TEHRAN (Reuters) - Iran's top legislative body, seeking to calm days of public fury over a disputed presidential election, has invited the three losers to discuss their complaints on Saturday, its spokesman said on Thursday. A spokesman for the 12-member Guardian Council said it had begun "careful examination" of 646 complaints submitted after the June 12 vote. President Mahmoud Ahmadinejad was declared winner with nearly 63 percent of the vote against 34 percent for his closest rival, Mirhossein Mousavi. Mousavi wants the vote annulled and held again. The council has said it is ready only to recount disputed ballot boxes. Council spokesman Abbasali Kadkhodai said Mousavi and fellow-candidates Mehdi Karoubi and Mohsen Rezaie could raise their problems at an extraordinary council meeting on Saturday. Yazdi, who heads the banned Freedom Movement and was foreign minister in Iran's first government after the revolution, was among scores of reformists rounded up since the election. Ahmadinejad defended the legitimacy of the vote, telling a cabinet meeting on Wednesday that it had "posed a great challenge to the West's democracy," Mehr news agency reported. "The ideals of the Islamic Revolution were the winners of the election," Ahmadinejad said, adding that 25 million of 42 million voters had approved the way he was running the country. The authorities reject charges that they rigged the vote, but scores of thousands of Iranians have braved riot police and religious militia to show their anger on the streets, ignoring Supreme Leader Ayatollah Ali Khamenei's call for national unity. "The friendly atmosphere that existed prior to the election should not turn into an atmosphere of confrontation and enmity afterwards, since both groups of voters believe in the Islamic system," Khamenei was quoted as saying in Kayhan newspaper. The supreme leader is due to lead Friday prayers, when Ahmadinejad supporters are expected to show their strength. The protests represent a challenge to the authority of Khamenei, who has usually stood above the factional fray. "His prestige has received a blow," said a senior Western diplomat in Tehran, who argued that Khamenei's call for unity had clearly failed to settle the showdown with the opposition. "Now the lines are drawn. He must give more to the opposition otherwise this will continue," the diplomat said, adding that he still expected a compromise that would preserve Iran's hybrid system of clerical rule and limited democracy. Hamid Najafi, editor-in-chief of Kayhan International, an English-language conservative Iranian daily, said the Guardian Council investigation of the vote would calm unrest. "I think that will be enough to pacify the opponents," he told Reuters. "After the investigation the Guardian Council will issue an official statement. That will be the final act." He said the overall election result would not change because "there isn't a millionth chance of doing any fraud" and Ahmadinejad's victory was "very obvious". Khamenei's Friday sermon would be "very effective for all these people who have been misled", he added. "Of course everything will calm down." Iran has denounced foreign criticism of the election, even though US President Barack Obama's administration has muted its comments to keep the door open for possible dialogue. The Iranian Foreign Ministry on Wednesday summoned the Swiss ambassador, who represents US interests, to protest at "interventionist" US statements on the country's election. The White House denied meddling, but said Obama would continue to defend the right of Iranians to protest peacefully.