Both sides will get half a loaf at the summit. The US and the Soviet Union both had to trim back expectations for the summit. But the meeting, with its INF treaty centerpiece, is aimed at sustaining arms control momentum.

American officials are already laying the groundwork for the first Soviet-American summit in Washington in 14 years. The Nixon-Brezhnev summit of 1973 yielded a new word for the superpower political dialogue: d'etente.

The Reagan-Gorbachev summit of 1987, which was announced at the White House Friday, is unlikely to be so momentous. But it could help set a pattern for superpower relations that will endure even beyond the Reagan years.

Soviet leader Mikhail Gorbachev is scheduled to be here on Dec. 7. The summit may last only three days. White House officials are considering, in addition to meetings in Washington, a brief trip to the presidential retreat at Camp David, Md., or to colonial Williamsburg in Virginia.

President Reagan has dropped his more ambitious plan of a ``see America'' summit, during which Mr. Gorbachev would have toured parts of the United States, much as former Soviet leader Nikita Khrushchev did in 1959.

And Gorbachev has dropped his insistence that the summit lead to some sort of ``understanding'' about limits on US plans for a nuclear missile defense system, the Strategic Defense Initiative (SDI, or ``star wars'').

The summit, then, will be less than what both sides wanted. But both will nevertheless see what they can get from the meetings.

One goal of the Soviets, according to a US official, is a rekindling of ``d'etente as they knew it'' - a lessening of superpower tension, continued negotiations toward nuclear arms limitations, and consultation and (when possible) cooperation on a wide range of mutual concerns.

The Kremlin, this official says, probably sees the coming summit as an opportunity to help usher in that era. The centerpiece of the summit - the signing of a treaty to abolish intermediate-range nuclear forces (INF) - will be showcased as the kind of fruit that US-Soviet cooperation can produce.

Few American analysts expect Gorbachev to refrain from pushing his opposition to SDI, however. But he may be taking a new tack, according to some US officials.

For some time, the Soviets have been pursuing a two-track strategy to oppose SDI. On the one hand, they have asked for specific limits on the kinds of weapons systems that could be tested as a part of SDI research. On the other hand, they have asked for a fixed US commitment to abide by a strict interpretation of the 1972 Anti-Ballistic Missile (ABM) Treaty, which - in the Soviet view - prohibits many forms of SDI testing.

But during the talks between US Secretary of State George Shultz and top Soviet officials in Moscow on Oct. 22 and 23, US officials noted that the former course - strict limits on SDI testing - seems to have been abandoned.

According to a US official who took part in the meetings, the Soviets seemed to have dropped the idea of a list that would specify the kinds of components that could be tested in space.

``The list wasn't talked about at all,'' he says.

On the other hand, another phrase was repeatedly used: ``strict compliance'' with the ABM Treaty.

The Reagan administration claims that the treaty language supports a ``broad interpretation'' that would permit expanded star wars testing; it has resisted taking a narrower view, as the Soviets are advocating.

Moreover, the ABM Treaty, although of unlimited duration, allows either country to withdraw with only six months' notice. A 10-year fixed commitment would, in the Soviet view, strengthen the treaty. But some US analysts believe that it would also give the Soviets time to nullify a US technological lead in SDI research and push ahead with its own space defense system.

It appears, then, that Moscow is still strongly opposed to SDI, but is attacking the program indirectly by making US compliance with the ABM Treaty the issue.

After the announcement of the summit last week, Soviet Foreign Minister Eduard Shevardnadze told a news conference, ``We are not speaking about SDI.''

Some US analysts now believe that the Soviets want to fashion a package of strategic arms reductions to hold out as the quid pro quo for strict compliance with the ABM Treaty. The reductions would total 50 percent of each superpower's nuclear arsenal, but the two sides disagree on how the cuts are to be made.

Mr. Shevardnadze, acknowledging the difficulties in forging a strategic arms agreement, said, ``At this stage, we shall focus on the problems of verification. ... We shall study in depth all aspects of verification'' of a treaty.

Verification details have yet to be completed on the INF treaty that Mr. Reagan and Gorbachev are expected to sign during the summit.

A US official says, however, that the INF agreement is much easier to verify than the prospective strategic arms reduction (START) treaty.

The INF accord would provide for a complete elimination of certain classes of medium-and short-range missiles from the Soviet and American arsenals. That means that even one such missile spotted by satellite reconnaissance would be grounds for demanding an on-site inspection to verify compliance.

However, under a START treaty, half of the strategic missiles on each side would remain active, and many of those would be on bombers and submarines. A satellite cannot discriminate between ``prohibited'' and ``permitted'' strategic weapons, the official explains. For that reason, he says, more emphasis will have to be placed on verifying the exact numbers of missiles in each side's arsenal, and the destruction of them once the treaty takes effect.