U.S. forces stepped up pressure on Shiite gunmen loyal to radical cleric Muqtada al-Sadr (search), pushing with tanks into the holy city of Kufa and assaulting militia positions in the narrow streets of a Shiite enclave in Baghdad (search). At least 34 Iraqis were killed.

The U.S. military also said a 24-year-old military policeman will be the first soldier to face a court-martial in the abuse of Iraqi prisoners at Abu Ghraib prison.

Spc. Jeremy C. Sivits, a member of the 372nd Military Police Company (search), has been charged with conspiracy to maltreat subordinates and detainees, dereliction of duty for negligently failing to protect detainees from abuse and cruelty and maltreatment of detainees, Brig. Gen. Mark Kimmitt (search) said.

The court-martial will be held May 19 in Baghdad, and Kimmitt said it will be open to the media. If convicted, Sivits faces one year in prison, demotion or a discharge for bad conduct, military officials said.

The rest of the seven soldiers charged in the abuse likely will face trials where they could get more severe punishments -- suggesting the military was starting the courts-martial with one of the lesser figures in the scandal.

The heaviest fighting in Baghdad came when militiamen from al-Sadr's Al-Mahdi Army (search) attacked police stations and set up checkpoints in the Shiite neighborhood of Sadr City, a heavily populated district in the eastern part of the capital, Kimmitt said.

U.S. troops moved in and secured two police stations in fighting that killed 18 militiamen, Kimmitt said.

Earlier, an explosion tore apart shops in a market in the western Biyaa district. The blast occurred when police tried to dismantle two bombs found in vendors' stalls, witnesses said. Four people were killed and 17 were wounded, the Health Ministry said. Kimmitt said three people were killed.

"Is this the freedom that they want -- people cut into pieces?," one man at the market, Fadhil Farid, cried. "What did we do wrong?"

At about the same time, gunmen opened fire on a U.S. patrol in western Baghdad, sparking a firefight that killed three Iraqi police, two civilians and one of the attackers, Kimmitt said. Fighters attacked another patrol in the center of the capital, wounding two Iraqi policemen.

On Sunday night, a bomb went off at the Four Seasons Hotel in central Baghdad, ripping through the bar and wounding six people, including two Iraqis, two British and two Nepalese, a hotel employee and police said.

The U.S. foray into Kufa was the deepest move yet into the city, an al-Mahdi Army stronghold. Several tanks pushed as close as 500 yards from Kufa's main mosque, trading fire with militiamen on both sides of the main road, witnesses said. Tanks also moved into the neighborhood on the other side of Kufa, trading fire with fighters.

Two civilians were killed and 10 others -- including two children -- were wounded in the battles, hospital officials said. Three houses were destroyed. The tanks pulled out of the city in the afternoon.

"It was the first time the Americans came this far," said Odai Abdulkarim, 24, a mechanic who has a shop off the highway leading to the Kufa mosque, where al-Sadr regularly leads Friday prayers. "We are afraid for our families, afraid the rockets would hit our house."

"Americans don't hit you if you don't hit them," interjected Haidar Abu Zaid, 35, another mechanic. "The al-Mahdi Army fires from our areas, so they have no choice but to fire at them -- and we end up getting hurt."

Also Sunday, scattered clashes occurred between U.S. and militia forces in the industrial area of Najaf, where al-Sadr sought refuge last month. Plumes of black smoke could be seen rising from the area. Iraqi police and U.S. tanks blocked the main road from Najaf to nearby Kufa, residents said.

The U.S. military has vowed to kill or capture al-Sadr and put down his militia, which has taken control of much of the holy cities of Kufa, Najaf and Karbala, south of the capital. But troops have been hampered by the nearby sites revered by Iraq's Shiite majority.

Still, U.S. forces have been moving more aggressively against al-Sadr fighters in their strongholds. U.S. troops raided the cleric's main office in Sadr City on Saturday night, detaining six people -- including a suspected al-Sadr lieutenant and financier, Kimmitt said.

He vowed that al-Sadr's movement would be put down in Sadr City, named after the young cleric's martyred father, a senior ayatollah.

"These are still some inside that district that are of the belief that Muqtada's militia can operate freely ... that somehow Muqtada has some sort of legitimate control over that district. They'll find out they're wrong," Kimmitt said.

Al-Sadr's militia fired mortar shells before dawn Sunday at the governor's office and other British positions in Amarah, 180 miles southeast of Baghdad, the scene of fighting the day before, a British official and residents said.

No British casualties were reported in that attack, but British spokesman Maj. Ian Clooney said "a number of possible mortar positions" were destroyed.

Several houses were destroyed in Amarah's Sadeq district, killing four civilians. Residents accused British helicopters of striking the neighborhood, but Clooney said no helicopters opened fire in the operation.

"There were helicopters circling the area, then they started firing," said Subeih Hassan, standing in front of his demolished house.

His brother was killed in the attack. The victims in nearby houses included an 8-month-old child, residents said.

In Basra, 100 miles south of Amarah, three coalition soldiers were wounded when a large explosion occurred near a coalition convoy Sunday morning, Clooney said. Witnesses said the wounded soldiers were British.

Elsewhere, a U.S. soldier was killed and another wounded Saturday in a mortar attack on a coalition base in the northern city of Mosul, the U.S. command said in a statement. Another soldier died in an "electrical accident," the command said.

The latest deaths bring to 765 the number of U.S. service members who have died since the U.S.-led invasion in March 2003. Of those, 557 died as a result of hostile action and 208 died of non-hostile causes.