"Obviously, they have a huge credibility gap with their own people as to the election process, and I don't think that's going to disappear by any finding of a limited review of a relatively small number of ballots," Clinton added.
Clinton made the comments at a press conference after Iran's Guardians Council confirmed the results of the June 12 presidential election following a partial vote recount.
Ahmadinejad has demanded that the United States recognize him as the democratically elected president of Iran, but Clinton said United States would refrain from drawing conclusions.
"We're going to take this a day at a time. We're going to watch, and carefully assess what we see happening," she said.
"This is a historic moment for Iran and for the Iranian people, and I don't want to, you know, speculate on how it's going to turn out," Clinton added.
The partial vote recount was intended to put an end to accusations of large-scale fraud that have been leveled by three of Ahmadinejad's electoral opponents -- Mir Hossein Moussavi, Mehdi Karoubi and Mohsen Rezai.
But the three refused to delegate representatives to participate in the recount, casting doubt on its impartiality, particularly because of the extent of the voting irregularities alleged.
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