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.

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.