U.S. air strikes killed 10 people in the eastern Baghdad militia stronghold of Sadr City, Iraqi police said on Thursday, but street fighting eased after four days of clashes that have killed close to 90 people.

The Sadr City slum has since Sunday been the focal point of battles between black-masked Mehdi Army militiamen loyal to Shi'ite cleric Moqtada al-Sadr and security forces.

An extension of clashes that erupted in late March when Prime Minister Nuri al-Maliki cracked down on the militia in the southern city of Basra, the violence has coloured a U.S. election-year debate over troop cuts by highlighting the fragility of recent security gains.

Iraqi police said two separate U.S. air strikes on Thursday morning had killed six people and wounded 10 in Sadr City. Lieutenant-Colonel Steven Stover, a U.S. military spokesman, confirmed two strikes on a suspected rocket site from a drone plane, but said he was unaware of any deaths.

Late on Wednesday, a U.S. helicopter fired two missiles at gunmen in the slum who attacked a joint U.S.-Iraqi security station, killing four, Stover said. Iraqi police and hospital officials said two of the four dead were young boys.

A roadside bomb also killed a U.S. soldier in central Baghdad overnight, raising the U.S. military death toll in Iraq to 20 for April, putting this month on track to be the deadliest for American soldiers since September.

Still, police, the U.S. military and residents said the streets of Sadr City, where most of the fighting this week has taken place, were calmer than in the past four days, when Sadr's militia battled the U.S. and Iraqi military.

NO GREEN ZONE HITS

"The situation is quieter. We are hearing sporadic gunfire and U.S. combat planes have been flying overhead, but the Iraqi military is not in the streets like past days," said Raad al-Humairi, a Sadr City resident.

"Some shops have opened. People buy what they need and then the shops close again."

For the first time in many days, the U.S. embassy said the heavily fortified Green Zone in central Baghdad had not sustained any rocket or mortar attacks from Sadr's militia.

On Thursday, U.S. and Iraqi forces raided a Sadr office in the town of Numaniya, south of Baghdad, seizing weapons and imposing a curfew, police said.

In a speech on Thursday, U.S. President George W. Bush, whose management of the war has been criticised by Democrats and Republicans, is likely to endorse troop reduction proposals by the U.S. commander in Iraq, General David Petraeus.

Petraeus wants to impose a 45-day freeze on withdrawals from July, when additional troops sent under the so-called surge are due to come home.

Petraeus "wants to wait and see. And I strongly support that," Bush told the Weekly Standard magazine in an online interview published before his speech. Bush is also expected to cut tours of duty for U.S. soldiers in Iraq and Afghanistan to one year from 15 months.

The Iraqi military plans to lift a two-week-old vehicle blockade in Sadr City on Saturday.

The blockade has prevented cars from entering or leaving the eastern Baghdad district of two million people, leading to piled up rubbish, food and medicine shortages, and what residents have described as a sense of claustrophobia.

Despite a one-day Baghdad-wide car ban imposed on Wednesday, the fifth anniversary of the capital's fall to U.S. troops, over 20 people were killed in Sadr City clashes and the U.S. military announced the deaths of 5 more of its soldiers.

U.S. military deaths have averaged roughly one a day over the past six months, but that number has doubled in April.

Maliki defended the Basra crackdown on Thursday after Petraeus told Congress this week that the Iraqi operation, under which 1,000 Iraqi troops refused to fight, was ill-prepared.

"We will not negotiate with the gangs," Maliki told a meeting of political leaders. "They (the gangs) have tried to call me and they continue to do this, but I reject them."