TEHRAN, Iran — Iran's supreme leader, long a critic of the United States, praised the U.S.-backed constitutional referendum in Iraq as "blessed" Friday and urged Iraqis to participate in December's parliamentary elections.

Delivering a prayer sermon at Tehran University, Ayatollah Ali Khamenei condemned those behind the daily bombings in Iraq, comparing them to former Iraqi dictator Saddam Hussein, whose mass-murder trial began this week.

"What is the difference between those who detonate bombs and kill people today and Saddam, who is on trial for killing people in the past?" Khamenei asked.

"Those who blow up mosques and kill Shiites are neither Sunni nor Shiite," he said, referring to the two main Muslim sects. "They are against Islam."

Khamenei has often condemned the U.S. invasion of Iraq, saying Washington only has itself to blame for the difficulties its forces face in the country.

On Friday, however, he said the Oct. 15 referendum on the Iraqi constitution was a "great and blessed job."

The Iraqi electoral commission said Friday that 63 percent of Iraq's registered voters had cast ballots in the referendum, a turnout higher than expected. The results of the referendum have been delayed by a vote audit.

In his sermon broadcast live on national TV and radio, Khamenei urged Iraqis to vote in December's general elections.

Iran, a Shiite-dominant nation, wields considerable influence over the Shiite majority in Iraq.

The United States has accused Iran of meddling in Iraqi politics and supplying weapons to the insurgents. Iran denies the charges.