Vice President Biden said Sunday that there are "real doubts" about whether Iran's presidential election was free and fair, but the United States has to "accept" Mahmoud Ahmadinejad as the winner for now. 

The vice president, speaking on NBC's "Meet the Press," stressed that monitors and officials do not yet have enough information to gauge whether the results are accurate but said several factors raise serious questions about the credibility of the vote. 

"We don't have all the details. It sure looks like the way they're suppressing speech, the way they're suppressing crowds, the way in which people are being treated, that there's some real doubt about that," Biden said. "I think we have to wait and see, but it didn't seem to be on its face to be as clear cut." 

Ahmadinejad said at a press conference Sunday that the vote was unquestionably "real and free," though reformist candidate Mir Hossein Mousavi accused the government of voter fraud. The clash has led to unrest in the streets, as Mousavi supporters clash with police in Tehran. 

Ahmadinejad compared the protesters to angry fans after a soccer match at which their team loses. 

But Biden noted irregularities, like the president's high percentage of votes from city voters which were not considered to be his base. 

The vice president tried to follow a careful line, however, given the administration's attempts to engage Iran. 

"I have doubts, but we're going to withhold comment until we have a thorough review of the whole process," he said. 

Asked about recognizing Ahmadinejad's claim of victory Biden said, "We have to accept that for the time being. But there's an awful lot of questions about how this election was run. And we'll see. We're just waiting to see. We don't have enough facts to make a firm judgment." 

Biden acknowledged the U.S. was disturbed by the Iranian government's suppression of free speech and crackdown on crowds protesting Ahmadinejad's re-election. 

The violence spilling from the disputed results has pushed Iran's Islamic establishment to respond with sweeping measures that include deploying anti-riot squads around the capital and cutting mobile phone messaging and Internet sites used by Mousavi's campaign. 

Biden said the United States is doing "everything we can in our power" to get to the bottom of the results. 

There was no indication that Washington was pulling back from it's desire for increased contacts despite the possibility that the outcome of presidential vote in Iran was predetermined by Ahmadinejad and his allies in the ruling clerical establishment. 

But the outcome of the election and the crackdown on citizens' ability to protest was sure to be seen as a setback for Obama policy of engagement with the Islamic Republic from which the United States has been estranged since the religious leadership took power four decades ago, ousting the U.S.-allied shah. 

Secretary of State Hillary Clinton said Saturday she hoped the outcome reflects the "genuine will and desire" of Iranian voters. 

The Associated Press contributed to this report.