President Clinton knows what he wants to do on domestic policy. On foreign policy he does not. He knows only that he wants to do good. It is a dangerous impulse.

It is particularly dangerous in the Balkans, a swamp of historical grievances, a place that produces more history than it can consume. Clinton came upon the Balkans and decided that he wished to do better than Cyrus Vance and David Owen who, after five months of negotiations, finally produced a peace plan.On Feb. 1, Vance and Owen brought their plan to the United Nations hoping the Great Powers would endorse and impose it. Clinton did not bite. He left Vance and Owen hanging for 10 days, then had Secretary of State Warren Christopher announced the appointment of a special American envoy to "attempt to build on the Vance-Owen negotiations in a way that can move toward a just, workable and durable solution."

This is a polite way of saying that the Vance-Owen plan was none of the above. It is also a way of announcing to the Balkans - and to the world - that the Americans have arrived. Thank you, Cy. Thank you, Lord David. Good work, chaps. But not good enough. We are taking over.

The talks are reopened and it is no secret why. The Vance plan, alas, does not meet American standards of justice. Clinton wants a settlement that is tougher on the bad guys (the Serbs) and easier on the good guys (the Muslims).

But when you take over a negotiation, you become responsible for it. You become responsible for reaching an agreement. You become responsible for enforcing it. Whatever outcome emerges from our meddling will be disguised as a mere improvement on Vance-Owen. But make no mistake. It will have "made in America" stamped all over it.

The first, grievous cost of such activism is coming into view now: the prospect of American ground troops in Bosnia. During the campaign and the transition, Clinton opposed U.S. troops in Bosnia. Why the switch? "Americans on the ground was the price of admission if we were going to ask folks to renegotiate a peace settlement," an administration official told the Washington Post. "We had to put some of our people in harm's way."

For the privilege of meddling in Vance-Owen, we put American soldiers in harm's way. To get shot at in Sarajevo - quite a price to pay for a diplomatic entree. Had we simply endorsed the Vance-Owen plan without Americanizing it, we could have insisted that since it was negotiated on behalf of Europe, Europe (and Russia) should back it up with troops, while the United States - a backer but onlooker - would contribute only air power. Now that we have appointed ourselves to the talks, such modesty is impossible.

We had a chance to establish the limits of our involvement. No longer. It is our game now. As of last Wednesday, the United States is committed to a Bosnian settlement. If the talks fail now, it is our failure. If they succeed, it will be our job to enforce it.

Why are we seeking responsibility for Bosnia, a crisis not of our making and far beyond our capacity to fix? Who rules where in Bosnia is not a vital U.S. concern. It is a European concern. That is why the current negotiators represent the European Community (Owen) and the United Nations (Vance). Why not then endorse a plan (Vance-Owen) that the most interested regional parties, Europe and Russia, have agreed upon?

Because, it seems, we wish to do better. Aggression ought not be rewarded.

A noble impulse, but costly. The fact is that the Serbs are the stronger party. No peace can be imposed unless they acquiesce, or unless we are willing to use overwhelming force to make them ac-quiesce.

The Vance-Owen plan already requires the Serbs to give up about 40 percent of the land they now control. The Vance-Owen map has large shaded areas of territory that must be given back. Almost all are areas that the Serbs are to give back to the Muslims and Croats.

Yet the Muslims have rejected the plan. They want much more. And Clinton at his town meeting Feb. 10 pledged not to force an agreement on the Muslims. The Serbs will resist any anti-Serb adjustment of Vance-Owen. Who will compel them? And if the Russians then cast a Security Council veto, shall we intervene unilaterally?

The one saving grace of Christopher's multistep plan is the decision to send our negotiator to Moscow. And to send him there before he goes to the United Nations to pick up the peace talks.

With any luck, Russia - historically, ethnically and religiously linked to Serbia - will curb the administration's anti-Serb enthusiasm and steer us back to where we were a couple of weeks ago when Vance and Owen brought their plan to the United Nations.

Saved by the Russians - another Balkan paradox. Let us hope so. Because without Serbian cooperation and, by extension, without Moscow's approval, there is no possible settlement in Bosnia short of massive American intervention. Anyone for that?