MANILA, Philippines (AP) _ The United States offered $502 million in annual aid to the Philippines for continued use of military bases in the country, but Manila said it wasn't enough, the foreign secretary said today.

Foreign Secretary Raul Manglapus made the disclosure at a news conference, two days before his scheduled departure for the United States to discuss the matter with U.S. officials.

He was asked to comment on reports quoting unidentified U.S. State Department officials as saying the United States offered an annual $489 million aid package in exchange for use of the six military facilities.

''It would have to be unacceptable,'' Manglapus said. ''It is probably insufficient.''

Manglapus said the offer actually totaled $502 million and was made by U.S. Ambassador Nicholas Platt when the two sides resumed negotiations over the bases in August.

The talks were recessed Aug. 17 because Platt had to go to Washington for consultations. The two sides said the talks are expected to resume this month.

Negotiations began in April and were to have lasted three months. But they dragged on and finally broke down over Philippine insistence that Washington pay $1.2 billion annually for Subic Naval Base, Clark Air Base and four smaller installations.

Asked if he would insist on the same figure when he meets with U.S. officials, Manglapus replied, ''Oh, yes. We shall be clarifying that our position is reasonable.''

Manglapus is to meet Secretary of State George Shultz, Defense Secretary Frank Carlucci and members of Congress.

Under an agreement that expires in 1991, the United States gives the Philippines $180 million a year through 1989. The talks are to determine the amount of compensation for the remaining two years.

Sources close to the talks say the Americans refuse to give in to the Philippine demands because of uncertainty they will be allowed to keep the bases after 1991.

President Corazon Aquino, who is under pressure not to renew the pact, has not disclosed her position. She says she wants to keep her options open until 1990.