BAGHDAD – The four-year U.S. military death toll in Iraq passed 3,500 after a soldier was reported killed in a roadside bombing in Baghdad. A British soldier was also shot to death Thursday in southern Iraq, as Western forces find themselves increasingly vulnerable under a new strategy to take the fight to the enemy.

The British ambassador to Iraq, meanwhile, signaled his government was ready to talk to those behind the abduction of five Britons in Baghdad last month. Iraqi officials have said they believe the Britons were taken by the Mahdi Army militia, which is largely loyal to the radical Shiite cleric Muqtada al-Sadr.

In a rare televised interview, al-Sadr blamed the United States for Iraq’s woes, often referring to it as “the occupier” and accusing it of being behind the sectarian violence, the growing schism between Iraq’s majority Shiites and once-dominant Sunni Arabs and economic hardships.

“We are now facing a brutal Western assault against Islam,” he said, draped in his traditional black robe and turban. “This agenda must be countered with a cultural resistance,” he said.

The mounting U.S. casualties, most by makeshift bombs placed in potholes on roads or in fields where troops conduct foot patrols, come as American troops work with Iraqi forces on the streets and in remote outposts as part of a joint crackdown on sectarian violence.

A U.S. soldier was killed and two others were wounded Wednesday when a roadside bomb exploded during combat operations in a southwestern section of Baghdad, the military said Thursday. At least 3,501 U.S. service-members have been killed since the beginning of the war, according to an Associated Press count.

They include at least 23 American deaths during the first six days of June – an average of almost four per day, a similar pace to that in May. American troops deaths reached 127 in May, making it the third-deadliest month since the war started in March 2003. The average is nearly double the roughly two a day killed in June 2006.

A British soldier also was shot to death and three others were wounded Thursday while on patrol in southern Iraq, according to Britain’s Ministry of Defense, pushing to at least 150 the number of deaths reported by the British military.

Separately, the British ambassador to Iraq, Dominic Asquith, appealed to the kidnappers of five Britons to release them or open negotiations.

The five – four security guards and a consultant – were abducted from the Iraqi Finance Ministry on May 29 by some 40 heavily armed men who then rode off with them in the direction of the sprawling Shiite district of Sadr City.

Iraqi officials say the Mahdi Army may have grabbed the men in retaliation for the killing by British forces of the militia’s commander in the southern city of Basra.

“I ask those holding them to release them so they may return to their families,” Asquith said. Then, in a clear offer to consider demands, he added, “We have people here in Iraq who are ready to listen to any person about this incident, or any person who may be holding these men and who may wish to communicate.”

The Mahdi Army, which fought U.S. forces in 2004, has been blamed for many of the sectarian attacks in Iraq. The U.S. accuses Iran of fueling the violence by providing weapons and training fighters.

On Thursday, al-Sadr said he maintains “friendship and good relations” with Iran but rejects any interference by Tehran in Iraq’s affairs.

“I must maintain friendship and good relations with Iran but nothing else,” he said.

The anti-American cleric dodged a question about his disappearance from public view during which he was believed to have been in Iran.

The interview on Iraqi state television was believed to be al-Sadr’s first since he re-emerged in public nearly two weeks ago. The program, which aired Thursday, was taped Sunday at his office in the holy city of Najaf, according to his aides. Al-Sadr had dropped out of sight at the start of a U.S.-Iraqi security crackdown in February.

Despite the crackdown, bombings, shootings, mortar attacks and execution-style killings left at least 63 Iraqis dead nationwide Thursday. They included 32 unidentified men who were handcuffed, blindfolded and shot to death in Baghdad – the apparent victims of so-called sectarian death squads usually run by Shiite militias like the Mahdi Army.

Gen. David Petraeus, the top U.S. commander in Iraq, stressed it was too early to see results because the buildup of some 30,000 extra U.S. forces for the operation would not be complete for nearly two more weeks.

“We achieved some early success through the first several months of the effort. The sectarian murder and execution rate was cut by over two-thirds, and then we saw it come back a bit during the month of May,” he told CNN.

“We do have some aggressive plans to … go after al-Qaida and some of the sanctuaries they’ve been able to build and dispatch car bombs from for some time. That won’t be without a fight, but it is something that we must do in the areas around Baghdad to provide better security for the people in Baghdad,” he said.

The day’s deadliest attack was a simultaneous suicide bombing of a bus and a truck in the town of Rabia, near the Syrian border.

The truck exploded at a police station, killing at least five policemen and five civilians and wounding 22 other people, including 14 policemen, according to army Capt. Mohammed Ahmed.

A guard shot the driver as he approached the building, but the truck still penetrated its blast walls and exploded, destroying the one-story structure, said Ahmed, an officer with the army’s Third Division, which oversees the area.

Another bomber driving a minibus struck a building about 500 yards away at the same time, according to police officials who spoke on condition of anonymity because they feared retribution. They said five Britons working in the building were wounded. British officials could not immediately be reached to confirm that report.

In Baghdad, a bomb beneath a parked car exploded at lunchtime outside a falafel restaurant, killing at least seven people and wounding 14, police reported. The teeming slum, which is a Mahdi Army stronghold, has repeatedly been targeted by Sunni extremists seeking to terrorize the Shiite majority and inflame hostilities between the Muslim sects.

Iraqi journalist Sahar al-Haidari, 45, was shot to death while she was waiting for a taxi Thursday in a predominantly Sunni area in the northern city of Mosul. Al-Haidari covered political and cultural news for the independent Voices of Iraq news agency and was the second employee of the organization to be killed in little more than a week.