The closer we get to a new SALT II agreement, the more popular it becomes to play war games with the present and future capabilities of U.S. strategic weapons and those of the Soviet Union. Who wins these war games depends, obviously, on what's being counted in -- or out. When the agreement's critics are playing, quite naturally, the Russians always win.

But that's in large part due to the fact that, in the critics' calculations, key elements in the U.S. force are conveniently forgotten or underplayed. We have seen good examples of this in two recent critical analyses of the pending SALT agreement. Or perhaps I should say one-and-a-half recent analyses, because the second fed on the first for a good part of its information.

The first was the Dec. 30, 1978 lead editorial in the prestigious Economist of London, which proposed that the period covered by SALT II "could be the beginning of seven singularly dangerous years" because of what it alleged were serious Soviet advantages over the United States.

The second was a Jan. 22, 1979 Newsweek column by George Will which, using selections from the Economist article, went on to say that Soviet weapons development since the mid-1960's had gone on unanswered by the United States.

Both of these analyses of strategic forces give the Soviets more and the United States less than each deserves.

The Economist, for example, focuses on three "large future problems" for the United States.

The first is the "large imbalance in Russia's favor described in part as "... by 1985 the United States will be behind Russia both in the overall total and in the most important sub-cate-gories" of missiles. The "most striking example is 'modern large' missiles where the Russians will be allowed to keep their 308 huge 10-war-head SS18s but the Americans will have none at all."

To start from the last first, the Soviets do not now have "308 huge 10-warhead SS18s," and they probably never will.

The most recent intelligence reports indicate slightly more than 100 SS18s existed after four years of installation, and a good number of them had only one warhead. U.S. intelligence experts expect that SS18s may eventually take the place of all the 308 SS9s that once existed, but there is no certainty of that. And as for the warheads, two of the three versions of the SS18s have only one warhead, and though the 8-10 warhead version is expected to be the "largest number" deployed, it will be far from the only one.

The United States has never had a "modern large" missile such as the SS9 and its successor, the SS18 -- but that was because it chose not to build one. That choice still stands. Even the proposed MX ICBM would be "small" by these standards.

Where the Soviets went for big rockets that could deliver heavy warheads, U.S. advanced technology permitted small, more accurate warheads to be built.

As U.S. missile accuracy increases, the need for a large warhead -- which always was marginal in these most powerful of weapons -- diminishes to almost zero.A 350-kiloton warhead delivered on target will destroy an enemy missile silo just as well as a two megaton warhead that is 10 times larger.

The Economist then enlarged the Soviet advantage by presenting a 1985 estimate of the total amount of destructive power that could be dropped on the United States, deriving from it advantages such as "a lead of 3 to 2 in their ability to destroy protected targets."

At a time when either side, because of accuracy, would need only one or two missiles to knock out the other's missile silo, what difference will it make if they have three to do that job and we have two?

Finally The Economist points to the political advantages to the Soviets "even if these figures [on missiles] were not militarily important..." If American nuclear power, it says, "is seen to be getting smaller than Russia's" -- thanks in part to faulty analyses such as this -- "public opinion in these allies will grow more nervous... and nervousness could crack the alliance."

Of course, in making the United States weak, The Economist left out the one major missile area where the United States remains far ahead -- total warheads.

Its numbers analysis also totally ignored the vast qualitative advantage of U.S. nuclear subs over Soviet versions and the U.S. bomber fleet armed with cruise missiles.

The second "and most dangerous place for... mistrust to grow" over SALT II, according to The Economist, is the fact that the treaty doesn't say anything about Soviet SS20 missiles aimed at Western Europe nor Russia's "Europebusting (Backfire) nuclear-bombing aircraft."

The editorial also reports the SALT II three-year limitation on deployment of a ground-launched nuclear cruise missile and suggests the Soviets will successfully "bully Mr. Carter or his successor into prolonging" it.

The Economist, in its analysis of how bad the European situation looks, makes no mention of U.S. nuclear systems there that for almost 20 years have been able to strike the Soviet Union and are not limited by SALT I or SALT II -- in particular U.S. and NATO allied forward-based tactical fighter planes, more than 200 of which are always on 15-minute alert at the end of runways armed with nuclear bombs.

No mention was made, either, of the U.S. aircraft carriers in the Mediterranean that have fighter-bombers that could be armed nuclear for Soviet homeland strikes. Nor did it include the U.S. Poseidon submarines assigned to the European theater whose missiles with their 10 or 14 nuclear warheads could also reach Russia.

In its handwringing over the cruise missile limitation, The Economist left out that the United States is building and testing not only a 1,500-mile cruise missile but also an extended-range Pershing missile. The new Pershing, with its 1000-mile range, would not be limited by SALT II if its production and deployment were somehow needed within the next three years.

Finally, The Economist wailed that the "biggest problem" with SALT II was that it "may leave the United States itself vulnerable to a surprise Russian attack."

Needless to say, this idea hinges on a theoretical Russian ability by the early 1980s "to destroy virtually all of America's land-based missiles in a single half-hour cataclysm, while still keeping quite a lot of its own missiles in reserve, ready for a second blow."

In the first place, it would take more than two hours for the so-called Soviet first strike -- time enough for any president to determine an attack had started and make a response using untouched land-based missiles.

Secondly, the United States would still have its sub-based deterrent force -- a factor never once mentioned in the entire Economist editorial. Since the submarines are never mentioned, the main element of the U.S. nuclear force does not have to be dealt with.

George Will, using The Economist, and a smattering of other sources, develops a theory that since the mid-1960s, the United States "has based arms-control policy on the hope that the Soviet buildup is merely a reaction to U.S. arms, and can be restrained by unilateral U.S. restraint." The resulting American weakness, Will argues, stems from failing to match Soviet increases.

To support this thesis, Will overlooks the substantial advances in U.S. strategic weapons development that have taken place since the mid-'60s and continue to this time.

For example, he makes no mention of the American development of more than one warhead on its missiles -- the so-called MIRVing which was developed in the late '60s, announced and deployed in the 1970s.

He leaves out the sharply increased accuracy of U.S. guidance systems and the decision in the early 1970s to make 300 of our land-based missiles so precise and powerful that they could knock out Soviet missiles.

Also ignored by Will is development of the Trident I long-range sub-launched missile, the highly accurate, bomber-launched cruise missile, the development of the MX missile and the Trident II and a variety of strategic defensive systems that keep us far ahead of the Soviets.

Will accuses American liberals of being blind to Soviet weaponry; he and The Economist are playing the same game, but with the formidable U.S. force.