American officials recently disclosed a plan to reduce U.S. troops in South Korea by a third over the next 18 months. Such a move was overdue and welcome, though the process for doing it needs work.

A half century after the U.S.-North Korean war, no peace treaty has been signed and both sides still keep troops massed at the demilitarized zone that divides North and South. But no one expects any future hostilities to begin like the war in the 1950s, with an invasion by North Korea’s army of more than 1 million.

Still, the United States has had 37,000 soldiers permanently stationed in the South as a “trip wire” in case of a North Korean ground attack. For some years, the perceived threat has been, not on the ground, but from North Korea’s small but growing arsenal of nuclear weapons.

The planned U.S. withdrawal of 12,500 of its 37,000 troops there is intended partly to relieve the strain on American armed forces heavily engaged worldwide, especially in Iraq. It is part of a restructuring ordered by Defense Secretary Donald Rumsfeld to reduce fixed foreign garrisons and add flexibility and mobility. Of the troops scheduled to leave South Korea, 3,600 already had been earmarked for relocation to Iraq.

A non-governmental task force of American specialists in Korean affairs suggested last year that the U.S. presence in South Korea be reduced and pulled back from the border through negotiations with the North for a pull-back of its forces from the frontier. Instead of taking that advice, the Bush administration has made what the North Korean officials consider a provocative move. They charge that the United States is simply getting its own forces out of the way in case it launches a nuclear strike against the North.

North Korea’s anxieties have been sharpened by Mr. Bush’s listing of North Korea as part of an “axis of evil,” his policy of pre-emptive warfare against perceived threats, and his plan to develop a new class of nuclear weapons to penetrate underground defenses.

The planned partial withdrawal thus has become a confrontational move rather than part of the current series of talks aimed at a negotiated resolution of the dispute over North Korea’s nuclear weapons program.

Selig S. Harrison, a Washington-based scholar who has just returned from his eighth visit to North Korea, organized the task force that presented a plausible plan for easing the crisis. He sums up this latest U.S. action by saying, “You can do the right thing for the wrong reasons. This is being done for the wrong reasons.”