A man brandishing a handgun briefly held a military guard hostage at the Tomb of the Unknown Soldier in Arlington National Cemetery yesterday evening, and was subdued when an Army officer knocked him to the ground with a ceremonial saber, military officials said last night.

Police identified the man as Robert K. Whitbeck, 36, an Air Force veteran who lives in Virginia Beach. He was listed in fair condition at the National Hospital for Orthopaedics and Rehabilitation in Arlington, where he was treated for facial lacerations that were apparently caused when his glasses shattered.

No one else was injured in the incident, which occurred after the cemetery was closed to visitors, said Lt. Col. Jamie Walton, press spokesman for the Military District of Washington.

U.S. Park Police said they knew of no motive for the incident. Spec. 4 David A. Nicholson, one of the tomb's guards, said the man had asked for a special ceremony and an Army staff car. Nicholson said the man appeared intoxicated and was weaving noticeably. "I was really surprised," said Nicholson, who had just gone off his guard watch when the incident occurred. "I thought it was just a joke at first."

Walton said the incident occurred at 5:35 p.m. as guards from the 3rd U.S. Infantry (The Old Guard) were practicing for a wreath-laying ceremony.

A man wearing a business suit stepped over a low chain fence and approached Cpl. Michael E. Kirby, who was standing at attention in the guard booth next to the tomb, which sits atop a hill overlooking Washington.

Kirby placed his M14 rifle at port arms, a readiness position, and started to advise the man that the cemetery is restricted military property after 5 p.m. when the man pointed a small-caliber handgun at him, Nicholson said.

Kirby continued to stand at attention while the others ran to guard quarters and alerted authorities.

Military officials declined to say whether Kirby's bayonet-tipped rifle was loaded.

Nicholson said Lt. Joseph Gerard, one of the soldiers practicing for the ceremony, was able to overpower the man about 10 minutes later by swinging the handle of a three-foot-long ceremonial saber at him, knocking him off his feet and shattering his glasses.

Another soldier pulled the pistol from the gunman's hand.

Dorothy Whitbeck, the wife of the man hospitalized under guard following the incident, told the Norfolk Virginian-Pilot newspaper last night that her husband "always talked about being buried in Arlington Cemetery."

She said he had been an Air Force airplane mechanic in Vietnam and was honorably discharged in 1970.

She also said he told her he had been held captive by the Vietcong for 13 days before escaping and returning to his base before anyone missed him.