TEHRAN, Iran — President Mahmoud Ahmadinejad added new fuel to an intensifying spat with President Obama Saturday, denouncing what he called "insulting" comments about a crackdown on protesters, and two opposition presidential candidates rejected participation in a special committee aimed at resolving the disputed June 12 election on the government's terms.

In televised remarks to judiciary officials Saturday, Ahmadinejad struck back at Obama a day after the U.S. president praised protesters for showing "bravery in the face of brutality," described violence against them as "outrageous" and said opposition leader Mir Hussein Mousavi has "captured the imagination" of Iranians who want a more open society. Obama also dismissed Ahmadinejad's demand for an apology for previous criticism and suggested that the Iranian leader apologize to the families of those who have been arrested, beaten or killed in the crackdown.

Noting that Obama has spoken of "reforms and changes," Ahmadinejad asked, "Why did he interfere and comment in a way that disregards convention and courtesy?" He said Western leaders who made "insulting and irrelevant comments will be put on a fair trial" by Iran at international gatherings.

"It is enough," he said. "Do not disgrace yourself further by such language and behavior."

Ahmadinejad also vowed to take a tougher approach toward alleged meddling by the West during his second four-year term, which the government has said will begin this summer.

"Without a doubt, Iran's new government will have a more decisive and firmer approach toward the West," Ahmadinejad said. "This time the Iranian nation's reply will be harsh and more decisive" to make the West regret its "meddlesome stance," he said.

Iran's Interior Ministry has proclaimed Ahmadinejad the winner of the June 12 election with nearly 63 percent of the vote, followed by Mousavi with less than 34 percent. Mousavi, 67, who served as prime minister for eight years in the 1980s, has charged that massive fraud "reversed" the results, cheating him of victory, and supporters have staged a series of street protests to back his demand for annulment of the election and the holding of a new one. Iranian authorities, including the supreme leader, Ayatollah Ali Khamenei, have ruled out a new vote and declared the demonstrations illegal. Security forces have been deployed to break up protests with clubs, tear gas, arrests and, on at least two occasions, gunfire.