President Reagan has outlined a formula for military interventionism that will steadily erode America's position in the world. The invasion of Grenada proves only one thing: that the world's most powerful nation can successfully invade the world's weakest country.

This action was taken over the strong protest of our ally, Britain. Our action has been greeted by an 11-to-1 vote against it in the U.N. Security Council and by demonstrations in Mexico, whose goodwill is of key imporannce to the United States.

Despite their denunuciation of the invasion, I suspect the Kremlin leadership is delighted by this display of American interventionism, for President Reagan has provided the occupiers of Afghanistan with an example of Soviet-style diplomacy.

Significantly, American war correspondents were denied access to the battle area for the first time in our history. The exclusion of the press represents another troubling hint of Soviet behavior, and deprives the nation of a full account of the facts.

The president sees every conflict--El Salvador, Nicaragua, Lebanon and Grenada--as a sideshow to the conflict between America and Russia. But if every Russian and every Cuban disappeared today, the "violent uncertainty" in the Caribbean and the Middle East would continue. If Mr. Reagan persists in sending arms, military advisers or Marines into every Third World upheaval, he will destroy America's standing in the world, bankrupt our Treasury, and--worst of all--sacrifice the lives of young Americans and young revolutionaries in the developing world. We have neither the capacity nor the responsibility to serve as the world's policemen in trying to suppress all the unrest around the globe. What we do have is the ability and the obligation to set a higher standard for the world to follow.