With U.S. troops mustering in the Persian Gulf and the nation on the cusp of war with Iraq, Americans in overwhelming numbers oppose unilateral U.S. military action, a national poll conducted last week for Knight Ridder newspapers found.

Many survey respondents said President Bush has not effectively explained why military action might be required. Nearly one in five said they still do not believe that Iraq poses a serious threat to the United States.

A robust majority of Americans -- 83 percent -- would support going to war if the United Nations backed the action. But support for war dwindles rapidly without U.N. approval.

Fewer than half of the respondents said they would support an attack on Iraq if the United States were joined by only one or two key allies. And 59 percent said they would be opposed to an attack if the United States decided to go it alone -- a switch that presents the Bush administration with a political and diplomatic quandary.

Perhaps this accounts for the huge numbers of anti-war activists planning to descend on Washington next weekend to protest the war. At least 100,000 are expected to participate. As one of the movement's leaders said, "The most important thing politically for us is to shatter the false myth of consensus . . ."