It seems that every American politician has his idea of linkage. In April, Sam Nunn urged that an INF Treaty be linked to reductions in the Soviet tank force. Jack Kemp wants INF linked to rectification of Soviet violations of previous treaties. Robert Byrd advised Mikhail Gorbachev that Senate ratification of the INF Treaty would be helped by a Soviet announcement of withdrawal from Afghanistan.

The problem with free-for-all linkage is that, given the number of things we want from the Soviets and the number of things they want from us, the number of possible permutations on linkage is infinite. And too much linkage yields none: the Soviets will never know which linkages we are really serious about. Instead, they are likely to conclude that linkage is simply the American way of sinking -- and then blaming the Soviets for sinking -- reachable agreements by tying them to unrelated and impossible demands.

Linkage is an important tool in dealing with the Soviets, but to be effective it must be used sparingly and logically. The cardinal rule must be: link like with like.

1. Link arms control to arms control. The president is now in a position to conclude a dramatic START agreement. The distance between his SDI position and the Soviets' -- whether or not to permit testing in outer space during the next seven to 10 years -- is small. Moreover, the Soviet position is the same as the Senate's. It is being imposed on the administration regardless.

Time to cash in the chip. But for what? For two things. First, a dramatic cut in Soviet land-based ballistic missiles, which pose the threat of surprise (first-strike) attack. At the Washington summit, Reagan asked for that and didn't get it. In return for agreeing to live by the narrow interpretation of the ABM Treaty for seven to 10 years, the United States should insist on a strict sublimit for warheads on land-based missiles.

Second, link the SDI/ABM concession to a new agenda for arms control -- namely, no more nuclear talks until the major nonnuclear arms issues are resolved. Until we have settled the questions of chemical and biological weapons and the imbalance of tanks and artillery on the central front in Europe -- no more talk about nukes. No talk of further reducing our strategic nuclear deterrent. And no talk of eliminating battlefield nuclear weapons in Europe.

Pressure is already building in West Germany to get rid of battlefield weapons. And it is a supreme Soviet objective to encourage the denuclearization of Germany in the hopes of neutralizing and detaching it from the Western alliance. Our price for SDI testing must be Soviet agreement to table all talk of further nuclear reductions.

2. Link regional issues with regional issues. The Soviets know they can no longer win in Afghanistan. What they have to show for their efforts is, in the words of one diplomat, "socialism in one city." They want out. The longer they wait to withdraw, the longer they bleed. They want a deal.

Why should we give it to them? We should say to Gorbachev: Afghanistan is your problem. You got in, you get out. You were no help to us in Vietnam, and we believe in reciprocity. It is in our interest to see you leave Afghanistan by helicopter off the roof of the Soviet Embassy in Kabul. We want a rout, not a settlement.

You want our help to prevent a rout in your back yard? Then you help us in ours. You want a settlement rather than a defeat in Afghanistan. We want a settlement rather than a defeat in Nicaragua. We will use our leverage to guarantee a nonaligned, neutral Afghanistan if you use yours to help guarantee a noncommunist Nicaragua. Our opening demand: cut off military aid to the Sandinistas.

3. Human rights. On arms control and regional conflicts, there is some symmetry between the superpowers. On human rights there is none. We cannot link their human rights issues to ours because they deny their people freedom and we don't. Nor does it make sense to link human rights to arms control or to regionalconflicts. No president will or should re-fuse an arms control treaty because oflow emigration rates from the Soviet Union.

Our leverage on human rights must be nonmilitary and nonstrategic. Trade, for example. Fortunately, the necessary law, the Jackson-Vanik Amendment, is already on the books. It needs only to be guarded against those ready to deal it away for Gorbachev's sunny smile. If the Soviets show themselves more humane to their captive populations, we will reciprocate economically.

Linkage is a good idea but only if you don't mix linkages. Don't link arms control with human rights. Or regional conflicts with trade. And don't link INF with anything. That treaty is done. The time to think about linkage is before you sign, not after.