MONROVIA, LIBERIA, JUNE 1 -- President Samuel Doe pleaded with the United States and other allies today to help end a revolt that threatens his government. Doe also promised not to seek re-election next year, an apparent attempt to appease rebels nearing the capital.

A U.S.-based spokesman for the rebels said they were no longer insisting that Doe surrender and stand trial for alleged corruption and atrocities, but demanding only that the president leave Liberia.

The spokesman, Tom Woewiyu of East Orange, N.J., said his statements had been approved by Charles Taylor, leader of the rebel National Patriotic Front of Liberia that was advancing on Monrovia on two fronts. If Doe left Liberia, Woewiyu said, the rebels would be willing to work with the remaining government to set up an interim one.

"I wish to announce here today my firm decision not to stand for the 1991 general elections," said Doe, a 40-year-old former army master sergeant who seized power in a bloody 1980 coup. "I am a leader, not a destroyer."

The main column of the rebel force has moved to within 25 miles of Monrovia, with rebel troops encamped near the international airport, which remained open. Employees, including ground crews, have not been showing up for work, however.

The capital is beginning to feel the effects of the rebel advance. Rice, a staple, is in short supply; many market shelves are empty; power outages have become frequent, and there has been no running water for two days.

More than 1,000 people, many of them civilians allegedly slain by government troops, have died since Taylor invaded this West African nation from neighboring Ivory Coast last Christmas Eve. The rebels took Liberia's port city of Buchanan, 95 miles southeast of the capital, a week ago.

Citing "deteriorating conditions," the State Department Wednesday night ordered nonessential U.S. government personnel and all dependents out of Liberia and advised private U.S. citizens to leave the country immediately. U.S. Embassy officials here said there are about 2,000 Americans in Liberia.

The Defense Department has dispatched a six-ship amphibious group carrying 2,100 Marines to the Liberian coast in case an evacuation of U.S. citizens is required.

{In Washington, a Pentagon source said the flotilla will arrive "probably Saturday."}

{In London, the British Defense Ministry said a British warship and a support tanker are "in the region and would be available to support any United States evacuation if required," Reuter news agency reported.}

At a news conference today, Doe asked for help from other nations.

"I hereby appeal to our traditional friends, the United States government and other friendly countries, to bring to an end this six-month-old, Libyan-backed incursion in order to pave the way for a peaceful, free and fair election in 1991," he said.

Doe said he had survived 35 or 36 coup attempts and would be happy to leave the "burden of leading a country" to somebody else.

The coup that brought Doe to power ended rule of the country by elitist descendants of freed American slaves who founded the nation in 1822. It became Africa's first independent nation in 1847.

Taylor, 42, served as head of Liberia's government purchasing agency but fled in 1983 to escape charges of embezzling $1 million. He was arrested in Massachusetts for extradition to Liberia on the embezzlement charges but escaped.

The rebel leader denies guilt, saying, "I skipped from jail to escape Doe's lies." He said all charges against him would be dropped if he overthrows Doe.

Taylor also has denied persistent reports that Libya is supporting his revolt.

Taylor spent the 1970s working as a mechanic at a plastics factory in Boston before graduating with an economics degree from Bentley College in Waltham, Mass.

He has made frequent use of the media, placing telephone calls to the British Broadcasting Corp. and other news organizations.

In an interview last month, the rebel leader said he wanted to assure the United States, Liberia's main foreign aid donor, that he is committed to good relations.

"The United States has permanent interests in Liberia, and not permanent friends," he said. "I would hope that we would have a real good marriage and a real honeymoon."

But his declarations on democracy have provided little cheer to the opposition parties that had been contesting Doe's power. Taylor said he would not share power with opposition parties.

"Don't think we are going to turn the government over to someone to screw up," he said. His plans, he said, do not include elections for at least three years and perhaps five.

He invaded Dec. 24 with about 200 rebels. Since then, his army has mushroomed to a force that diplomats put at about 4,000 fighters.