WASHINGTON (AP) _ Deaths from ''friendly fire'' are common in the rocket and missile battles of complex modern warfare. Even Persian Gulf commander Norman Schwarzkopf recalls being ''bombed by our own Air Force'' in Vietnam.

In the gulf, a U.S. military investigative team was trying to determine whether some of the 11 Marines killed in a battle with Iraqi troops Tuesday were accidentally hit by American or allied forces.

One Pentagon source said Friday the rationale for the investigation includes the fact that a hole in one of the Marines' vehicles came from a 30mm gun, the weapon aboard the Air Force's A-10 antitank ''warthog.'' The source spoke on condition of anonymity.

In Tuesday night's fighting, Marines and Iraqis squared off in close ground fire, at times coming within 25 yards of each other, pool reporters said.

The military team is investigating the possibility that some of the Marines died from a missile fired by a U.S. warplane that struck a U.S. light armored vehicle.

During the Vietnam War, there were 90 friendly fire incidents caused by bombing from the air and artillery on the ground, according to a study by Army Lt. Col. Charles R. Shrader. That compared with 173 in World War II.

The military doesn't break out casualty figures resulting from U.S. troops accidentally firing on their compatriots.

The Pentagon's official figure for U.S. service personnel killed during the Vietnam War is 58,151, of whom 47,355 died directly in combat. The remaining 10,796 are listed as ''other,'' which means deaths due to aircraft accidents, drunken driving, suicides - and friendly fire.

Schwarzkopf was a target of friendly fire in one Vietnam incident and was bitterly blamed for causing a death in another, which was highly publicized.

''I was bombed by B-52s one time in Vietnam,'' he told reporters at a briefing in Riyadh, Saudi Arabia, last Sunday. ''They were coming towards us. They did a marvelous job of dropping all their bombs, and then one (bomb) rack hung up and it released over my position.''

During Schwarzkopf's second Vietnam tour, he commanded an infantry battalion in which a young GI was killed by a U.S. artillery shell that went astray. The incident was the basis for a book and a movie called ''Friendly Fire''.

They relate how an Iowa farm couple, outraged by the death of their son, Sgt. Michael Mullen, become fervent opponents of the war and blame Schwarzkopf for covering up alleged irregularities in the young man's death.

Author C.D.B. Bryan, who did extensive interviews with Schwarzkopf, vindicated him of wrongdoing and described him as a man deeply disturbed by the tragedies of war.

''War is a profanity, it really is,'' Schwarzkopf is quoted as saying. ''It's terrifying. Nobody is more antiwar than an intelligent person who's been to war.''

Soldiers in Saudi Arabia, Kuwait and Iraq could be especially prone to friendly fire incidents, since it can be difficult to identify troops or locations in the desert.

Friendly fire casualties occurred during the Soviet Union's war in Afghanistan, where the Soviets bombed their own troops in the desert.

Around 20 percent of Israeli casualties in Lebanon in 1982 were said to be due to friendly fire.