WASHINGTON (AP) _ The assassin's bullet that killed U.S. Army Col. James ''Nick'' Rowe in the Philippines passed through a soft-spot in his armored car, the Pentagon announced Thursday.

Spokesman Dan Howard told reporters that the slaying of Rowe on his way to work in suburban Manila last Friday demonstrated the limits of the precautions the U.S. military can take to protect its personnel overseas.

''Our bases in the Philippines have had a heightened state of alert for over a year and a half now since three Americans were shot outside of Clark Air Force Base,'' said Howard. ''That alert status continues. And of course, the shooting has reemphasized the need for all of our people to be especially vigilant.''

''Other than the heightened alert, there is a limit to what can be done.'' he said.

The car in which Rowe was riding was armored, he said, but ''perhaps there's misunderstanding about what an armored vehicle is. ... It's an ordinary passenger automobile which has been provided with some types of protection. It is not an M1A1 tank.''

Thick plexiglass is applied to the windows, and armored plates are in the doors as well as extra shielding in the floor, he said.

''But it is not a completely secure conveyance,'' he said. ''And if someone fires armor-piercing rounds with an automatic weapon at the vehicle, it can find a soft spot. It's not impervious to that sort of an attack.''

In fact, the bullet that killed Rowe ''was not an armor-piercing round,'' Howard said. ''The round bullet that entered the Rowe vehicle went through what they call a non-hardened area around the window frame.''

Police in the Philippines said hooded gunmen sprayed Rowe's car with an M- 16 rifle and a .45-caliber pistol. The communist New People's Army claimed responsibility for the slaying.

Rowe, 51, was chief of the ground forces of the Joint U.S. Military Advisory Group, which provides training and logistical support to the Philippine military.

''We use these armored vehicles all over the world, at our embassies and the like, military installations, as do many, many other governments,'' Howard said, adding that there was no investigation under way to see whether the Rowe vehicle was deficient.

Howard said no special precautions were being taken in the Philippines as a result of the slaying.

''It's been a general precaution area there,'' he said. ''The New People's Army has a long history of terrorist activity against citizens of the Philippines. They have occasionally turned their violence on foreigners.

''We had three military personnel killed a year and a half ago. There have been some other incidents, one of which was ... the blowing up of some radio towers. But there's no indication of a widespread campaign.''

He said U.S. officials have alerted Americans in the Philippines, adding, ''We have a great many people there.''

Howard said he didn't know whether special investigators had been sent from the United States on the case.

''Obviously, this is sovereign territory of the Philippines,'' he said. ''We are cooperating with the Philippine authorities. And we are pleased with the high level of cooperation that we're getting, trying to investigate the matter.''

Howard said Rowe would be buried Monday afternoon at Arlington National Cemetery, across the Potomac from Washington, D.C., following a private funeral in Ft. Myer Memorial Chapel.