Succumbing to pressure from the White House, Senate Foreign Relations Committee Chairman Richard G. Lugar (R-Ind.) agreed yesterday to head an official U.S. team to observe the Feb. 7 Philippine presidential election.

Lugar said that, despite his "significant reservations" about the fairness of the campaign, he thinks that this country should send such a delegation. At a news conference yesterday, he said "it would be a serious mistake for the United States not to demonstrate its support for democracy in the Philippines." He said the presence of American observers at the election could contribute to that goal.

Lugar said he had reached that conclusion despite misgivings about whether the campaign, which has been rife with charges of intimidation and illegal activities by supporters of President Ferdinand Marcos against challenger Corazon Aquino, "will reflect the genuine political will of the Filipino people."

But he added that he has the impression from Filipinos seeking to promote democracy and reform that "the presence of Americans will be a help to anyone who wants to keep the fraud down to a dull roar."

Even more importantly, Lugar said, "I believe that the United States should have an official presence at the election to show our interest and kinship with the Filipino people. An official American delegation will demonstrate our support for democracy in the Philippines."

Several members of the House and Senate have been outspoken in arguing that no members of Congress should join the delegation because Marcos might try to portray it as giving a U.S. stamp of approval for his reelection.

In response to repeated questions about that danger, Lugar said, "We should not certify the validity of the elections process nor place a seal of approval or disapproval on its result. That is up to the Filipino people.

"I still have eyes to see and a mouth to speak," he said, adding that if the U.S. delegation detects irregularities, "We would point out that we suspect fraud is occurring."

Lugar said his reservations about the Philippine situation include Marcos' retreat from promises to retire Gen. Fabian Ver, the armed forces chief who is viewed as a symbol of military corruption and political interference, reports of violence, intimidation and manipulation of the election machinery to favor Marcos' candidacy and restrictions on foreign observers that could prevent their getting an accurate picture of whether the balloting is fair.

He said he had conveyed these concerns to the Philippines' acting Foreign Minister Pacifico Castro in a meeting Thursday, adding that the Filipino emissary told him that "some flexibility might be possible" in the arrangements for official foreign observers.

The Reagan administration, which is eager to maintain strategically important U.S. naval and air bases in the Philippines, has become increasingly concerned about the Marcos government's failure to counter a growing communist insurgency. As a result, the administration believes that a high-level observer delegation will serve as a reassurance to the Filipino people that the United States supports their aspirations for far-ranging political, economic and military reform.

Congressional and administration sources said that Secretary of State George P. Shultz called Lugar to tell him that Marcos had extended an official invitation for the delegation through Castro. Shultz also said that Reagan wanted Lugar to lead the delegation, and they began discussions on who to appoint as members.

Administration officials say they hope to come up with a delegation composed of about 20 members of Congress and 20 private citizens. However, Lugar said, "It's fair to say that members of Congress are not beating down the doors to get on the delegation."

House Foreign Affairs Committee Chairman Dante B. Fascell (D-Fla.), whom the White House had wanted to serve as cochairman with Lugar, said yesterday that while he agrees that the United States should send a team of observers, he does not intend to take part.