Presidents Bush and Mikhail Gorbachev at the White House Friday will sign what officials say is a "clear statement" of agreement on the central elements of a strategic arms accord, as well as understandings on other new arms limitations, against a political backdrop that has subtly diminished the importance of what they have achieved.

The removal of Soviet forces and influence in Eastern Europe, the dramatic improvement in U.S.-Soviet relations and a declining interest in military spending have played a larger role in curtailing the historical East-West confrontation than the arms negotiations to be celebrated Friday, according to U.S. officials and independent experts.

These sources emphasize that rather than representing a diplomatic or superpower breakthrough, the accords symbolize the art of the possible -- in this case, a mutual constraint made possible by a new spirit of political cooperation that follows years of difficult relations.

These officials and analysts say that the accords on nuclear testing and chemical, conventional and strategic arms are primarily expected to influence military activities over the long term, by protecting both sides against an unexpected reversal of the current budget-driven trend toward disarmament.

"Arms control has declined in relative terms as an important element of the U.S.-Soviet relationship," a senior U.S. official said. "The Soviet disengagement from Eastern Europe, and everything that flows from that, has turned out to be more significant than anything the negotiators have done."

Under the accord on strategic nuclear arms to be approved in its major elements by the two presidents, for example, U.S. and Soviet arsenals will each shrink by several thousand warheads. A major portion of the U.S. reduction is driven by the Bush administration's recent decision to scale back its planned purchase of B-2 strategic bombers in the face of congressional opposition to the weapon's high cost.

The accord will require substantial reductions of Soviet land-based missiles, which many officials of the Bush and Reagan administrations considered a significant threat to U.S. security. The deployment of other strategic weapons in the Soviet arsenal can be expanded, however, and the United States can also produce thousands of nuclear-tipped cruise missiles, submarine-launched missiles and aircraft-delivered bombs.

The accord on conventional or non-nuclear arms, on which Bush and Gorbachev will try make new progress during the forthcoming meetings, calls for elimination of about 130,000 tanks, artillery, armored vehicles and aircraft in Eastern and Western Europe. It also would require a 26 percent reduction of U.S. troops and a 65 percent reduction of Soviet troops in Europe.

But Hungary and Czechoslovakia have already negotiated the complete withdrawal of Soviet forces from their territory by the end of next year, and the impending unification of East and West Germany is expected to complicate the long-term presence there of sizable U.S. and Soviet forces.

On chemical arms, the leaders will sign a bilateral agreement inspired by Bush that would eliminate most of their existing poison gas arsenals by the year 2002. Destruction of the U.S. stockpile was already required by Congress, however, and as one U.S. official said, "these weapons have never been considered that much of a military threat anyway because they are as likely to contaminate the user as the enemy."

In an important concession, the United States agreed that poison gas production will be halted in both countries as soon as the accord takes effect. But the Soviets quit several years ago, and the United States has been forced by congressional restrictions and a recent shortage of raw materials to substantially slow its program.

The leaders also will approve modifications to the monitoring provisions of treaties capping the explosive force of U.S. and Soviet underground nuclear tests. Both sides have asserted they complied with the treaties, which were signed in 1974 and 1976, but the Reagan administration demanded more intrusive inspections to guard against Soviet cheating.

"These agreements matter in that the two sides are finally finishing a very old agenda," said John Steinbruner, director of foreign policy studies at the Brookings Institution. "They have used all the remarkable events of the past year to resolve longstanding negotiating issues and ratify what's happening anyway. But there's nothing really venturesome here."

Perhaps the toughest arms control issue -- the future security arrangement for Germany, and by implication, the future of the existing military alliances -- is so new that discussions remain in a preliminary stage, and a solution may not develop quickly, U.S. officials say.

Several officials said three of the four new arms accords should be judged in part as starting points for more sweeping arms reductions if East-West relations continue to improve.

They said the Bush administration recently agreed in principle that the two sides should move promptly to additional negotiations on strategic arms, although the sides have not settled on language inscribing this agreement. They evidently also have not agreed whether the new talks should begin after an initial treaty is signed, as the Soviets have proposed, or when it takes effect.

U.S. officials also say that the bilateral chemical accord will speed progress on a global treaty requiring elimination of all poison gas stockpiles and allowing much more intrusive monitoring, which has been under negotiation for more than a decade.

In an effort to satisfy Soviet demands for constraints on the German military force, the Bush administration has also indicated that the new conventional arms accord, which limits only U.S. and Soviet troops in Europe, is the precursor to a subsequent agreement that will also constrain allied troops.

U.S. officials distinguish between reducing these armaments and accepting further limitations on nuclear testing, however. "No one within the government has spoken favorably of moving in the immediate future" to a reduction in the number or maximum explosive force of underground tests needed to develop new strategic weapons, as the Soviets have proposed, one official said.

The agreement to be signed Friday provides for direct monitoring of the force of at least two underground nuclear explosions a year in each country, to verify compliance with the longstanding ban on those with a force exceeding 150 kilotons, equivalent to 150,000 tons of TNT.

But in a provision that some U.S. officials fear could complicate future rejection of additional testing limits, the pact also allows each side to establish three scientific stations on the other's territory to measure the strength of seismic signals from underground nuclear tests. The officials say the provision will undermine U.S. arguments that additional limitations cannot be adequately monitored.

U.S. and Soviet officials say that progress on each of these issues was made largely through Soviet concessions, rarely reciprocated by the United States. The consequence is that most of the accords closely follow American drafts and reflect American preferences for strict monitoring, for limitations on the types of weapons where the Soviets have the greatest advantage and for exclusion of many weapons in which the United States enjoys a technological advantage.

"You know for such a long time, it was a free fall {by the Soviets}, whether it was in Eastern Europe, Lithuania, arms control or whatever," a senior U.S. official said in a recent interview. "It was exhilarating {because} they were looking at things as we would like them to look at things."

On the topic of nuclear-tipped cruise missiles, the official said by way of example, the United States gave up "virtually nothing. The Soviets wanted to ban cruise missiles {and} we can essentially have all we want." The winged, low-flying drones require sophisticated electronics and computers, areas of technology in which the Soviet Union lags considerably behind.

The official noted that "it's been very tough slogging" in arms negotiations since April, when Gorbachev started "digging in" and demanding U.S. compromises as a "part and parcel" of an effort to stay in power. He added that while "the conservatives are trotting out" some arguments against these concessions, the accord will provide for "all of the flexibility that the Congress in its infinite wisdom . . . will let us take advantage of" in an era of sharply declining defense spending.