The United States and the Philippines are preparing to negotiate anew on an agreement governing U.S. use of two huge military bases here amid a shift of the moderate pro-western political opposition to a more radical stand in favor of abrogating the accord.

The shift reflects a drive for unity among political groups opposed to the government of President Ferdinand Marcos. But it also highlights the growth here of the antinuclear sentiment that has burgeoned in the United States and Western Europe, threatening to inhibit America's military arrangements with its allies.

Opponents of the vast air and naval bases argue that they not only are used to store nuclear weapons but that they also make the Philippines a likely nuclear target in a war between the United States and the Soviet Union. U.S. officials have refused to confirm or deny the storage of atomic weapons at the bases.

Talks to review a 1979 agreement on American use of Subic Naval Base and Clark Air Base were due to start in April but have been delayed by agenda and protocol problems, officials said. The review, in effect a renegotiation of parts of the agreement, is expected to start shortly although a date has not been set.

At the heart of the negotiations will be the question of U.S. compensation to the Philippines for use of the bases, officials say. But the Philippines also is raising the issues of its sovereignty over the facilities and their "social costs," a reference to the rampant prostitution, drug abuse and crime near the bases.

There is no doubt that the Marcos government wants to raise what it likes to call the "rent" for the bases, currently a $500 million aid package spread over the five years from 1979 to 1984. No new figure has been put forward officially, but Philippines newspapers have reported plans to demand $1.5 billion for the next five-year period. The 1979 agreement, due to expire in 1991 but subject to review every five years, formally gave the Philippines sovereignty over the bases, which have been American military preserves since the beginning of the century.

U.S. officials argue that the bases serve both countries' national interests and are especially vital in countering Soviet military expansion in the Pacific and Indian oceans.

Maj. Gen. Kenneth Burns, the U.S. commander at Clark Air Base, said recently that the Soviet Far East command now has 46 divisions, about 2,500 military aircraft and more than 200 major combatant ships and submarines.

He said Soviet ships and planes now have routine access to former American bases at Cam Ranh Bay and Danang in Vietnam, putting them within easy reach of the strategic Malacca, Sunda and Lombok straits between the Indian and Pacific oceans. He said half of the noncommunist world's oil supplies pass through these "choke points."

Opposition politicians reject such arguments, charging that the bases violate Philippine sovereignty and serve to buttress the "Marcos dictatorship."

"We want these bases out because the Americans are supporting Marcos," said former senator Lorenzo Tanada, chairman of the Anti-Bases Coalition formed to lobby for U.S. military withdrawal. "The Americans would not support Marcos if not for these bases." Tanada, who has opposed the bases since 1953, said a second argument is that "with these bases, we are open to nuclear attack by the Soviet Union."

He said the United Nationalist Democratic Organization, a coalition of moderate political opposition groups known here as Unido, had recently come around to his position, formally agreeing Friday to join a new coalition whose platform calls for removal of all bases.

The opposition politicians plan to announce the coalition at a rally on Philippine independence day, June 12, with a view to challenging Marcos' ruling party in parliamentary elections next year.

The Unido leader, former senator Salvador Laurel, confirmed that he has changed his position on the bases from willingness to respect the agreement until it expires in 1991 to insistence that the 1979 treaty be abrogated. However, he said he still opposes another demand by the anti-bases coalition--that U.S. Ambassador Michael Armacost and embassy political counselor Herbert Malin be expelled on grounds of interfering in Philippine affairs by making public speeches in favor of the bases. Armacost heads the U.S. negotiating team that is preparing for the bases talks.

Laurel said he changed his stand because "now it is very clear that Russian nuclear warheads are aimed at the U.S. bases in this country." He added, "It's also very obvious now that nuclear weapons are being stockpiled at the bases."

In addition, Laurel said, "we are tired of waiting for the U.S. government to stop propping up the Marcos dictatorship. We have waited a long time since 1972," when Marcos declared martial law, enabling him to remain in power beyond his second presidential term.

With the presence of U.S. nuclear arms at the bases uncertain and Soviet intentions unknown, the opposition on antinuclear grounds seems largely an extension of the fears that have gripped Western Europe recently over plans to deploy U.S. missiles, diplomats said. Although the bases have operated in much the same way for years, the anti-nuclear argument previously had not been strong enough to sway the main moderate opposition parties.

Regardless, the public continues to appear largely apathetic about the bases, except in the adjacent towns of Angeles and Olongapo, where the U.S. facilities are strongly supported as the principal sources of livelihood. Anti-bases demonstrations in front of the U.S. Embassy here in recent weeks have failed to attract more than 100-odd protesters at a time.

Opponents such as Tanada blame this lack of interest on Marcos' control over the press. But western diplomats believe it probably suits Laurel, who may have calculated he stood neither to gain nor lose votes by adopting the anti-bases stand.

As in past negotiations, the Marcos government appears to be using the local press to soften up the U.S. side for a "rent" increase. A rash of stories in Manila's main dailies last week raised the issue of "social costs" for the first time. They quoted the head of the Philippine negotiating team, Ambassador to Washington Benjamin Romualdez, as saying these problems would be a major topic for discussion.

"In particular, we have in mind places like Angeles and Olongapo, cities where the presence of tens of thousands of U.S. soldiers and sailors has created serious problems of crime, drug abuse, prostitution, health and sanitation and thousands of abandoned and neglected children of unwed mothers," Romualdez said.

He added: "The United States must share in the responsibility of improving conditions in those communities affected by the presence of its military installations." Filipino officials said nearly 8,500 "hospitality girls" in the two cities were treated for venereal diseases last year in government clinics.

However, the press campaign seems unlikely to reach the levels of vitriol attained during the Carter administration, when negotiations on a bases agreement bogged down over the compensation issue. Then, government-inspired demonstrations in front of the U.S. Embassy even included contingents of the ruling party's youth movement led by the president's daughter, Imee Marcos.

"There is reason to believe it won't be knock-down, drag-out horse trading this time, but a statesmanlike discussion between two defense partners," one U.S. official said, adding that both sides hoped the talks could be completed by early October so that financial aspects could be included in the next budget year.