Behind the Reagan administration's reluctance to speak out forcefully on the disputed presidential election in the Philippines is a growing belief that a strong endorsement of either side would precipitate violence and jeopardize the United States' strategic position in Asia.

"The election is much closer than we thought it would be," a senior official said. "We thought that any strong statement in either direction could set off a wave of violence."

Another senior official, discussing the situation in the Philippines in detail with editors and reporters of The Washington Post, said that "we have to, from a diplomatic view, walk a very tight rope."

"What do we say?" this official said. "If we say that it's been a very fraudulent election and should be thrown out, we have people in the streets tomorrow with riots and the like and burnings . . . . The next thing you know you have civil disorder. If we say it's not a fraudulent election, we'll have the same thing because indeed it is a fraudulent election."

He added, as President Reagan did is his news conference last night, that the evidence of fraud was circumstantial and probably could not be proved in a court of law.

On Monday, in an interview with The Washington Post, Reagan played down the importance of fraud in the election. But yesterday morning, the White House found itself confronted with sharp demands from many quarters of the administration calling for direct denunciation by Reagan of the way the government of Philippine President Ferdinand Marcos conducted the election.

Reagan met at 9:30 a.m. yesterday with Secretary of State George P. Shultz, Defense Secretary Caspar W. Weinberger, White House chief of staff Donald T. Regan and other high officials. They had before them a long cable from Stephen Bosworth, the U.S. ambassador in Manila, detailing a series of voting irregularities and violent incidents largely directed at the opposition party of challenger Corazon Aquino.

Administration sources said that in addition to this cable they had lengthy intelligence reports that said the situation in the Philippines was "unstable" in the wake of the election.

"The common view from all quarters was that the president had to speak out," one source said. He added that on this issue the "two frequent combatants," as he referred to Shultz and Weinberger, were in complete agreement.

This message was reinforced late yesterday morning when leaders of the official U.S. observers of the election, Sen. Richard G. Lugar (R-Ind.) and Rep. John P. Murtha (D-Pa.), joined the meeting and added strongly worded accounts of fraud in the election. A similar view was conveyed by White House counsel Fred F. Fielding, another member of the observer delegation.

Lugar and the others stressed that Reagan should not call the entire election a fraud because this would tempt Marcos to invalidate it and stop the counting, which would be virtually certain to ignite violent demonstrations in the Philippines. Instead, they urged that Reagan speak critically of the fraud -- as he did last night at his news conference -- but withhold judgment on the validity of the election.

Sources said that some officials at the State Department proposed a toughly worded statement that included a reference to U.S. aid to the Philippines. But the sources said that these officials were generally satisfied when Reagan accepted the proposal that Philip C. Habib, the respected former envoy to the Middle East, be sent to the Philippines to make an assessment.

Late last year Reagan sent Sen. Paul Laxalt (R-Nev.) to deliver a warning to Marcos to reform his government and deal seriously with the threat of a communist insurgency. Sources close to the president said that Laxalt delivered the message but told Reagan when he had returned that Marcos intended to reform his government and military establishment.

"Habib will not sugarcoat his findings," a senior official said last night.