Secretary of Defense William Cohen ordered the reopening of the Tomb of the Unknowns in Arlington National Cemetery in Virginia Thursday so that the remains of the soldier who died in Vietnam can be removed, tested and, very likely, identified.

Next Thursday, after painstaking preparations, the steel coffin bearing the unknown soldier's remains will be lifted from the crypt, draped in an American flag and taken under military escort to the forensic laboratory at the Walter Reed Army Medical Center in Washington.Although details are still being worked out, the Pentagon plans to hold a simple, solemn ceremony during the exhumation at what is one of the nation's most revered sites, just over the Potomac River from the capital.

The remains will undergo a battery of tests, including sampling of mitochondrial DNA, a method of identification not available to the military's forensic scientists when the remains were classified "unknown-26" after the Vietnam War.

The Pentagon believes the new technologies will likely show that the bone fragments belong to one of two pilots shot down over South Vietnam on May 11, 1972.

Cohen's order followed a recommendation made last week by a group of Pentagon officials who spent four months investigating the circumstances surrounding the selection of the remains. That investigation began after the family of one of the two pilots, 1st. Lt. Michael J. Blassie, appealed to the Pentagon to open the tomb, believing that it contained his remains.

But forensic tests suggest the remains could belong to an Army helicopter pilot, Capt. Rodney L. Strobridge, who crashed on the same day as Blassie in the same battle over An Loc.