President Ferdinand Marcos has charged that the United States is "in default" on payments of military aid to the Philippines under an agreement on American use of military bases here.

He made the charge after a news conference yesterday when asked his reaction to a U.S. congressional move to trim $15 million from a military aid package for the Philippines. The cut has been portrayed here as a U.S. response to the reinstatement last month of the armed forces chief of staff, Gen. Fabian Ver, following his acquittal in the assassination of opposition leader Benigno Aquino.

"The United States is now in default of payment of $60 million up to 1985," Marcos said at Fernando Air Base near the town of Lipa in Batangas Province. He said that with the latest cut of $15 million, the "default" now reaches $75 million "as we count it."

The U.S. Embassy here denies that there has been any "default" on aid payments, which are linked to the bases as "compensation" for their use by U.S. forces. The Marcos government regards the aid payments as obligatory and often refers to them as "rent."

The Reagan administration has pledged its "best efforts" to provide $900 million in aid as compensation to the Philippines for the use of Subic Bay Naval Base, Clark Air Base and some smaller facilities.