KUFA, Iraq (Reuters) - Rebel Iraqi cleric Moqtada al-Sadr said Friday he could unleash suicide bombers if U.S. forces attacked the holy Shi'ite city of Najaf, and called on the whole nation to unite to expel Iraq (news - web sites)'s occupiers.

U.S. forces are poised just outside Najaf and have vowed to kill or capture Sadr and destroy his Mehdi Army militia, which has clashed with foreign forces across south and central Iraq.

Speaking at Friday prayers in Kufa, next to Najaf, Sadr told thousands of Shi'ites Najaf would never fall to the occupiers.

"We will shed blood to keep our holy city," he said. "Lots of believers, men and women, came to me and asked permission to become martyrs and to execute martyrdom operations.

"I keep telling them to wait. But if there was an assault on our cities or on our religious authorities we will be time bombs and will not stop before destroying enemy forces."

There are fears a U.S. attack on Najaf could spark a wider and bloodier uprising. Sadr likened Iraq's situation to that of the Palestinians, saying Iraqis faced the same enemies and must unite to defeat them.

"We should be united for one ultimate goal, to liberate our country and remove the filth from Iraq," he said.

The congregation chanted "Long live Sadr" and denounced not only the occupation forces but the U.S.-appointed Iraqi Governing Council, saying "America and the Council are infidels."...