If President Clinton is wise, he will confine himself to verbal saber-rattling and not send American troops into Haiti.

But if Clinton insists on invading, he had better not do so without the formal approval of Congress even though he contemplates only "consulting" the lawmakers and doubts even that step is necessary.No matter how Clinton goes about touching bases with Congress, it's hard to imagine him getting more than grudging acquiescence at best.

Americans, after all, have a long tradition of putting aside their differences and closing ranks behind the commander in chief during a military conflict. But the man in the White House can't always count on knee-jerk unity, particularly not under the present circumstances.

That much should be clear from the fact that a majority of this nation's lawmakers disapprove of an invasion. Even the Congressional Black Caucus, which has crusaded for restoring democracy to Haiti, has mixed feelings about sending in the troops.

Sentiment among the general public is even more clear-cut. A CNN-Time magazine poll shows only 23 percent of those surveyed approve of invading Haiti.

Most of the Pentagon brass think an invasion against Haiti's poorly trained and equipped army would be a snap but can't see how to bring the troops promptly home again without leaving that country as impoverished and troubled as before.

Even among the supporters of Jean-Bertrand Aristide, the democratically elected president whom Clinton is trying to put in power in Haiti, there are deep doubts about the wisdom of a U.S. invasion. Recently such groups have been staging regular demonstrations in front of the White House protesting U.S. intervention. Aristide himself is ambivalent about an invasion.

Moreover, whatever rationale there may be for an invasion has diminished sharply with the recent decrease in the flow of refugees from Haiti to the U.S. Their numbers have dropped from as many as 1,000 a day to only a trickle.

Under these circumstances, a decision to invade would at best put Clinton in the position of saying in effect that he knows best despite his lack of military experience and his comparative lack of interest in international affairs.

At worst, a White House decision to invade would raise suspicions that Clinton was putting the lives of American troops at risk merely to bolster his sagging ratings in the polls and overcome his reputation for waffling on important decisions.

If Clinton really thinks an invasion would improve his popularity by making him look firm and decisive, he should think again. The invasion of Panama, after all, didn't do much for George Bush's reputation or popularity. And after that invasion was over, Panama still had many of the same problems it had before.

Another important point involves the fact that Clinton went to the trouble of getting formal approval from the United Nations for an invasion of Haiti. If he does not also seek formal approval from Congress, Clinton will be in the indefensible position of preferring the views of foreign leaders to those of Congress and the American people.

When troops are sent into battle against the wishes of the public and many of their elected representatives, the results can include prolonged political infighting and morale problems among the troops that impair military effectiveness.

If Clinton wants to avoid such serious problems, he had better start courting both Congress and the public - and make a much better case for military action in Haiti than he has so far.