BAGHDAD, Iraq - A Marine amphibious assault vehicle on patrol during combat operations near the Syrian border hit a roadside bomb Wednesday, and 14 Marines were killed in one of the deadliest single attacks in Iraq against American forces.

A civilian interpreter also was killed in the bombing, which came two days after seven Marines died in the same area during combat with insurgents. At least 1,820 members of the U.S. military have died since the Iraq war began in March 2003, according to an Associated Press count.

The Marines killed today were assigned to Regimental Combat Team 2, 2nd Marine Division, II Marine Expeditionary Force (Forward), the military said. One Marine also was wounded in the attack.

The explosion occurred just outside Haditha, which is 140 miles northwest of Baghdad.

The Marines were riding in an amphibious assault vehicle, which is designed to carry troops from ship to shore and on land. It has a road speed of about 45 mph and can carry up to 25 Marines. It is not as heavily armored as the Bradley fighting vehicles that the army uses.

The names of those killed were not released.

The latest losses come on the heels of the deaths of seven U.S. Marines in combat two days ago in the volatile Euphrates Valley of western Iraq, where American forces are trying to seal a major border infiltration route for foreign fighters.

One of the Marines died in a suicide car bombing in Hit, 85 miles northwest of Baghdad. The other six were killed Monday in Haditha, 50 miles from Hit, while battling insurgents. They all were attached to the same suburban Cleveland unit.

The American deaths come as the Bush administration is talking about handing more security responsibility to the Iraqis and drawing down forces next year.

At least 39 American service members have been killed in Iraq since July 24 - all but two in combat. In addition, the Iraqi Defense Ministry said that since the beginning of April, more than 2,700 Iraqis - about half of them civilians - had been killed in insurgency-related incidents.

The extremist Ansar al-Sunnah Army claimed responsibility for killing the six Marines on Monday.

Masked gunmen showed up in the Haditha public market Monday afternoon displaying helmets, flak jackets and other equipment they said were taken from the bodies of the dead Marines.

Fighting has intensified in recent weeks in Haditha, Hit and other dusty towns along the Euphrates River as American forces step up efforts to seal off the approaches to the Syrian border.

The Marines launched a series of operations in the region in May and June in hopes of pacifying the area so Iraqi military and civilian forces could assume effective control. But the insurgents have proven resilient.