ON THE MISSILE issue, it's hard not to show some impatience toward the Belgians, whose prime minister was in Washington this week, and the Dutch, who are like the Belgians on the issue but more so. The two, NATO allies, have held back from making good on their formal NATO commitment to take a few of the American missiles now being deployed to counter new Soviet missiles targeted on Europe. While Soviet-American talks were either stalemated or broken off, the two countries lagged because the arms-control scene looked grim. Now that talks have resumed, some Belgians suggest it's best to hold off a bit longer "to give the talks a chance."

One has to acknowledge the basic situation of Belgium and the Netherlands. As small countries located well behind the East-West line, they know their military role is slight. They were drawn into the missile issue only because West Germany, the front-line country which was to take the largest share of the new American missiles, demanded company so that the response to the Soviet SS20s would be a broad alliance action, not a German- Soviet faceoff. As complicated multiparty democracies, Belgium and Holland do not find it easy to make difficult national security decisions. Nonetheless, each is struggling with deployment for the larger cause of alliance solidarity.

Perhaps the best that can be said is that the current Belgian and Dutch governments know their special (and very different) political circumstances and are working to honor their NATO obligations. The immediate interest is in Belgium, which is supposed to start its agreed deployments this year. The Dutch are only at the stage of considering construction of bases. Not much good will come out of outsiders' offering them hortatory tactical advice.

The United States, all the same, has a clear obligation as the leader of the alliance. It cannot dictate to its allies or threaten them. Still, it cannot afford to convey the impression that whatever they decide is just fine by Washington. An alliance that cannot follow through on its own deliberate decisions is an alliance in trouble.

The Kremlin failed to block the initial NATO deployments by walking out of the old INF talks. But it will surely try to halt or slow some of the later deployments by saying they will endanger the new talks. It cannot be stressed too strongly that the current tensions in Europe arose exclusively from unprovoked and provocative Soviet missile upgradings, which continue. The new NATO deployments are a belated and, so far, disproportionately small response, one meant first to put weight behind an effort to negotiate the threat down on both sides.