Speaking on Fox News Sunday, Secretary Rumsfeld blasted the election in Iran.
"The fact that they had a mock election, and elected a hard-liner ought not come as a surprise to anybody, because all the other people were told they could not run - it is against the law," said Mr. Rumsfeld.
U.S. officials, including President Bush, had denounced the elections beforehand, pointing out that more than one-thousand potential candidates, many of them reformers and women, were excluded by the Guardian Council, an unelected body of clerics that vets political candidates.
Tehran Mayor Mahmoud Ahmadinejad won a decisive victory in Friday's run-off election over his better known opponent, former President Ali Akbar Hashemi Rafsanjani, who had positioned himself as a moderate.
Mr. Rumsfeld said he did not know much about Mr. Ahmadinejad, but accused him of doing the bidding of Iran's conservative religious leaders.
"He [Ahmadinejad] is no friend of democracy,” said Mr. Rumsfeld. “He is no friend of freedom. He is a person who is very much supportive of the current ayatollahs, who are telling the people of that country how to live their lives. And my guess is, over time, the young people and the women will find him, as well as his masters, unacceptable."
Meanwhile, in Tehran, Mr. Ahmadinejad said he would head what he called a "government of friendship." He called for all political factions in Iran to put aside their differences and seize the opportunity to work together to develop the country.
He also paid his respects at the mausoleum of Ayatollah Ruhollah Khomeini, leader of the 1979 Islamic Revolution.
Mr. Ahmadinejad said he came to renew his allegiance to the founder of Iran's Islamic Revolution, and that he will continue along the path that Ayatollah Khomeini started.
On other issues, the Iranian president-elect said his government will continue nuclear talks with the European Union. But he emphasized that Iran will continue to develop nuclear power for peaceful purposes.
He also added that his government sees no significant need for improved ties with the United States. The Bush administration has accused Iran of secretly trying to develop an atomic bomb. Tehran denies the charge.