MANILA, JULY 1 -- Suspected Communist rebels kidnapped a U.S. Peace Corps volunteer shortly before all agency workers were ordered to evacuate the Philippines because of threats to their safety, American officials said.

U.S. Embassy officials here, however, repeatedly denied today that they knew of the abduction when they suddenly ordered the evacuation of all 261 Peace Corps volunteers in the Philippines last Wednesday. At the time, they cited intelligence reports that the Communist New People's Army (NPA) planned to kill or kidnap volunteers.

The kidnapping may signal a dangerous new phase in the increasingly violent campaign to shut six U.S. military facilities in the Philippines, analysts said today.

U.S. Embassy officials said several armed men took Timothy Swanson, 26, of Cheyenne, Wyo., from the remote Negros Island mountain village of Patag, not far from a rebel stronghold, on June 13.

They said the kidnapping was discovered when officials tried to inform him of the ordered evacuation, and it was not confirmed until Saturday.

{In Kennebunkport, Maine, President Bush on Sunday decried the kidnapping and told reporters, "We've been very much worried about this."

{Bush's national security adviser, Brent Scowcroft, told reporters that officials in Washington "first heard about it maybe a week ago, close to a week ago."}

The American officials said they had not heard from Swanson's captors and were unsure of their motives. But there was widespread agreement today that the kidnappers almost certainly were guerrillas of the NPA. Negros Island, 300 miles southeast of Manila, is a stronghold of the NPA, which has fought the government for 21 years.

One analyst who studies the NPA said today that the abduction signaled a raising of stakes in the rebels' drive to shut down the half-dozen American bases here.

"The NPA view just about any American in the Philippines right now as fair game," he said. Eight Americans have been killed in political violence here in the last 14 months.

All Peace Corps volunteers except Swanson were accounted for today, said U.S. Embassy spokesman Stanley Schrager. About 200 have left for Hawaii since Friday, Schrager said, and the rest will fly out at dawn Monday.

Schrager said several embassy aides rushed to the Negros Island provincial capital of Bacolod today. "There's no question in our mind that he was abducted by the NPA," Schrager said.

Fluent in the local dialect of Ilongo, Swanson spent more than two years in northern Negros, an impoverished sugar-growing area. A week after his abduction, guerrillas killed one militia member and four civilians in an ambush in Silay City, close to Patag.

Described by a friend here as "the most laid-back dude you can imagine," Swanson married a schoolteacher in Silay City on May 29 and planned to spend a third year working in a local forest nursery.

The Rev. Antonio Fortich, the retired Roman Catholic bishop of Negros, said in a telephone interview from Bacolod that about four rebels went to Swanson's home in Patag on the night of June 13.

"This group told the wife, 'We would like to borrow your husband,' " said Fortich, who is known to have had contacts with the rebels. "His wife said, 'You can talk to him here.' They said: 'No, the mountains are better. There it is very secluded and silent.' "

Asked what the rebels wanted, Fortich said: "They said they wanted to talk matters over with him. They have many gripes against the government."

As he was leaving, Swanson told his wife, Merle, "not to say anything" to authorities so they would not "blow up this news" and endanger his life, Fortich said.

She received a letter from her husband five days ago saying "he is all right" and asking for books, underwear and eyeglasses, Fortich said. The rebels took the bundle during the night.

Fortich said Swanson's wife finally told U.S. officials of his abduction when they sent a notice announcing the evacuation.