The United States and the Philippines signed an agreement today to exchange legal assistance in investigating questionable contracts that allegedly provided kickbacks to former president Ferdinand Marcos and his close associates.

The accord, called an "agreement on procedures for mutual legal assistance," was signed by Victoria Toensing, U.S. deputy assistant attorney general representing the criminal division of the Justice Department, and Jovito Salonga, the chairman of the Presidential Commission on Good Government, the Philippine body charged with recovering the "ill-gotten wealth" of Marcos, his relatives and associates. U.S. officials said the agreement was patterned after a 1976 accord between the United States and Japan to promote cooperation in investigations of the Lockheed bribery scandal.

The four-page accord signed today commits the U.S. and Philippine governments to share evidence in their separate investigations of alleged illegal activities involving the Westinghouse Electric Corp., Amworld, Inc. and Raymond Moreno, a Filipino businessman. The two sides also agree to help each other in arranging interviews with potential witnesses and locating additional evidence.

The government of President Corazon Aquino has said that Marcos, who was ousted in February, may have received millions of dollars in commissions paid by Westinghouse for the controversial $2.1 billion nuclear power plant project. Amworld and Moreno are under investigation in the United States for alleged involvement in kickbacks from more than $100 million worth of military contracts financed in part by U.S. aid. Commission sources here have termed Moreno a "front man" for former armed forces chief of staff Gen. Fabian Ver, a close Marcos associate who fled to Hawaii with Marcos in February, and Edna Camcam, a Philippine real estate dealer and socialite. Officials of the deposed Marcos government have identified Camcam as Ver's mistress.

In addition to Westinghouse, the mutual legal assistance agreement cites Burns and Roe Corp. as a subject of investigation, presumably also in connection with the nuclear plant project. Mentioned along with Amworld are Telecom Satellites of America and Digital Contractors, Inc. The three California-based electronics companies were reportedly set up by Moreno to do business with the Philippine military, winning lucrative communications contracts in 1982 and 1983.

The agreement also provides for extension of cooperation to other investigations by an exchange of letters between the two parties.

Today's signing came a day after the U.S. undersecretary of state for political affairs, Michael Armacost, filed an affidavit with a district court in Hawaii asking, in effect, for a stay of a June 6 ruling by U.S. Federal Judge Harold Fong. Fong, ruling on a lawsuit filed by Marcos' son-in-law, Gregorio Araneta III, ordered the release to Marcos of about $7 million in cash, jewelry and other belongings held by U.S. customs.

The affidavit, copies of which were released here, argued that the ruling cast doubt "on the ability of the United States to carry out its assurances to the Philippine government to hold the property until it can be placed in interpleader." An interpleader is a legal procedure for determining the ownership of disputed property by having a disinterested third party, which holds the property, put the matter to a court.

The affidavit said failure to fulfill these repeated assurances "would adversely affect bilateral relations" with the Philippines, which were "vital to the foreign policy interests of the United States."

Salonga said that while Armacost's appeal and the Hawaii proceedings were not related to today's agreement, the affidavit was "an important manifestation of legal assistance" being offered the Philippines by the United States.

The signs of increased cooperation came as the Salonga commission reported receiving feelers from several Marcos associates, known here as his "cronies," about cooperating in the search for "hidden wealth." Commission sources said one of those seeking to negotiate with the commission was Eduardo M. Cojuangco Jr., a close Marcos associate who ran a virtual coconut monopoly that ranked as a leading foreign exchange earner and generated more than $1 billion in controversial levies. Another former Marcos associate, Jose Yao Campos, was recently granted immunity from prosecution in return for cooperating with the commission and turning over more than $150 million worth of properties that he said he managed for Marcos.