The forces of anti-U.S. cleric Muqtada al-Sadr (search) in this holy Shiite city and neighboring Kufa braced Saturday for an American assault, with hundreds of men with assault rifles roaming the streets and guarding makeshift checkpoints.

In anticipation of violence and because of a major religious occasion this weekend, most stores in Najaf (search) and Kufa were closed. Some owners emptied shops of goods, storing them at home for fear of looting amid any violence, residents said.

No police or coalition troops from the Spanish contingent in charge of security in the two cities could be seen. U.S. commanders suggested they will move to seize Najaf and Kufa from al-Sadr's control after the Shiite ceremony of al-Arbaeen ends Sunday.

"I usually close my store at 10 at night or even later," said Salam Nasser, a grocer in Najaf's Prophet Street. "But for the past five days, I pull down my shutters at 4. We are frightened by all the tension."

About 1,000 U.S. troops backed by tanks swept into the southern city of Kut on Wednesday to expell al-Sadr militiamen. They met relatively little resistance.

Brig. Gen. Mark Kimmitt (search), deputy chief of U.S. military operations, appeared confident Saturday that American troops can do the same when they move against al-Sadr elsewhere.

"It is our assessment that the al-Sadr militia doesn't have the capability to conduct prolonged offensive operations," he told reporters in Baghdad. "Everytime his militia is faced with a determined resolve of Iraqi security forces or the coalition military forces, they typically will shoot a few rounds and run away."

Sheik Qays al-Khaz'ali, one of al-Sadr's top aides, promised a fight.

He also said he thought the risk of outrage among Muslims the world over would keep the U.S. military from battling al-Sadr's militia in Najaf and Kufa (search) — two cities with major Shiite holy sites.

"Frankly, we don't think that the occupation armies will have the audacity to do that," he told journalists at one of the movement's self-styled Islamic courts in Najaf.

Al-Khaz'ali, 30, and other al-Sadr supporters often wear a white coffin shroud — a Shiite custom to signal readiness for death — during Friday prayers as al-Sadr delivers sermons at Kufa.

"We are happy to die defending our leader," he told The Associated Press.

Najaf and Kufa are mostly made up of intricate networks of twisting alleys lined by small houses, meaning U.S. troops could face deadly urban fighting that could last for days.

Also, Al-Sadr's forces are deployed near the cities' Shiite shrines, and would have the advantage of fighting on their home turf.

Some two dozen heavily armed gunmen stood guard Saturday outside al-Sadr's office on an alley near the shrine of Imam Ali, a revered Shiite saint. They occasionally sang and danced, holding their rifles aloft, and chanted slogans expressing their readiness to die for al-Sadr, who is said to be holed up inside his office.

Other senior Shiite clerics in the city — most of whom eye al-Sadr's militancy with concern — were also bunkered down behind intensified security.

Guards of Grand Ayatollah Ali al-Husseini al-Sistani (search), Iraq's most influential Shiite cleric, erected a metal barricade in front of the alley where he lives and hung a black curtain over the alley's entrance. At least six armed men stood guard there, three times the usual number.

Al-Sadr has been a menace to U.S. occupation authorities in Iraq for almost a year, delivering anti-American sermons at the main mosque in Kufa and organizing al-Sadr's militia. He had generally refrained from calling for or even condoning armed resistance against U.S. forces, which meant he was generally left to his own devices.

Last week, however, he engineered a wave of mass resistance across much of the country after his movement's newspaper was closed down for allegedly inciting violence and one of his top aides was arrested on murder charges. Over the past week, his militiamen wrested control from coalition troops in a string of cities in central and southern Iraq.

But al-Sadr is unpopular in Najaf; his militiamen are looked down at by Najafis who see them and their leader as violent upstarts who lack the wisdom of the city's elder clerics.

With his al-Mahdi Army in control of Najaf, an ancient and prestigious seat of Shiite learning south of Baghdad, the 30-year-old cleric has realized a long-cherished dream. It may not last for long.