Vice President Walter Mondale gently suggested to Philippine President Ferdinand Marcos yesterday that political prisoners jailed under martial law be released to improve U.S.-Philippine relations.

Mondale's 90 minute private meeting with Marcos represented the hightest-level U.S. appeal for human rights improvement here in nearly six years of martial law, but Marcos made no promises to free his political opponents in prison.

Mondale said after the meeting that he had "pointed out the concern that the American people have toward the allegations affecting this nation, and how that could adversely affect our ability to improve, broaden and deepen the relationship" with the former U.S. colony.

One of the five anti-Marcos leaders who met with Mondale at his invitation later in the day said the vice president had indicated he discussed "in particular the prisoners" with Marcos.

In a press conference after the meeting, Marcos acknowledge that he and Mondale had "lively exchanges on the Phiippines human rights performance," and that Mondale had implied a release of prisoners would improve reltions.

But Marcos argued that allegations of human rights violations were not true and that "there are no political prisoners in the Philippines."

Of the estimated 500 to 2,000 people in jail for martial law-related offenses such as subversion, Marcos said, "nobody has been imprisoned . . . because of his political beliefs."

He said nothing about releasing four National Assembly candidates, who polled about one million votes each running on an anti-Marcos ticket in last month's election and then were jailed for leading a peaceful but illegal march against election abuses.

Marcos said he had no objection to Mondale's meetings yesterday with five Filipino dissidents and one American priest opposed to martial law here. Philippine security agents, however, stopped anti-Marcos assembly candidate Jerry Barican after he visited a U.S. press center in Mondale's hotel late Tuesday night and confiscated a Mondale press information kit Barican had picked up.

On the difficult issue of continued American use of Philippine military bases, Mondale and Marcos agreed to what is the first written statement of basic principles for a new agreement, including the Philippine right to appoint Philippine base commanders, the U.S. right to control its own personnel and vital parts of the bases involved, and the right to a review of any new agreement every five years.

Negotiators must still resolve troublesome issues such as criminal jurisdiction over U.S. servicemen and increased compensation for the bases.

Despite the attention he paid to human rights, Mondale appeared sensitive to complaints Marcos has made of one-sided American "meddling" in Philippine domestic affairs. The vice president complimented the Philippine people on their "deep faith in the importance of human liberty and justice' and made no specific public references to the jailed dissidents, the controlled local press or the lack of any check on Marcos' martial law powers.

Mondale's criticisms were indirect. During his toast to Marcos at a state banquet last night in Malacanang Place. Mondale said: "It is our firm belief that democracy is the most effective and humane way of reconciling differences and building the unity required of a modern nation."

At his late afternoon press conference, Marcos called Mondale a "polished diplomat." He said the vice president's approach to the human rights issue differed markedly from efforts by American officials in the past to alter his policy toward active political opponents.

In his meetings with Marcos' opponents Mondale saw James Reuter, an American Jesuit priest and long-time foe of martial law, for about 15 minutes.

Then five of the most prominent Filipino opponents of one-man rule arrived, including former Philippine president Diosdado Macapagal, former foreign secretary Salvador Lopez, former senator Gerardo Roxas, and two leaders of the Catholic church, Bishop Julio Labayan and Sister Irene Dabacus. Mondale also went to visit Jaime Cardinal Sin, the Manila archbishop who saves most of his complaints about martial law for private sessions with Marcos.

Labayen said Dabacus called during the group's 45-minute interview with Mondale for amnesty for political prisoners, action against cases of torture and respect for rights of national minorities, such as mountain tribes threatened by development schemes.

Lopez said "We spoke up in general for the release of all political prisoners against whom no charges have been filed." These would reportedly include the four anti-Marcos candidates whose April 9 protest march arrest is still being reviewed by military authorities.

According to his press secretary, Albert Eisele, Mondale told the dissidents in their closed-door meeting that he and President Carter "got elected because of human rights, and we're anxious the U.S foreign policy again be seen as a reflection of basic values.

The dissidents told reporters after the meeting they were pleased with what they heard.

Manila was the first to stop in a five country tour that will include Thailand, Indonesia, Australia and New Zealand. Members of Mondale's party said they felt it presented the most difficult problems given the base negotiations and the worldwide publicity generated by the latest round of arrests in Manila.