When the Pentagon’s latest “kill vehicle” slammed into a mock warhead 140 miles above the Pacific Ocean, the Bush administration and defense contractors cheered: National missile defense was one step closer to fruition.

They should have held their applause. This was only the fifth out of at least 20 highly controlled tests. Realistic conditions come later. The reality is that President Bush, even if he serves two terms, will likely be retired before any missile defense system is ready to be deployed – even if it works.

But ever since the beginning of the Bush administration, the concept of missile defense has taken on an urgency that has captured the attention of Congress and the press, damaged our relations with Russia and other allies, and blinded Americans to the real threats from abroad.

Some day, maybe, if all the technological problems are overcome, missile defense may be a military weapon. Yet it is already being deployed as a political weapon.

Consider Sept. 11. The devastating attacks on our country were low-tech, planned and executed by private terrorists. No “rogue states” were involved. But before you could say, “ICBM,” missile defense proponents were crowing that the attacks proved the need for missile defense.

It was a brilliant tactic. Opponents had decided to hold their fire after Sept. 11, lest they be viewed as exploiting a national tragedy. So the field of debate was left to the hawks, whose fuzzy assertions obscured the real message of Sept. 11: namely, that attacks on the United States are unlikely to come by ballistic missile, but by more conventional means.

This irony was on display again recently. On the very day the latest missile defense test results were reported, the press also announced that the administration was concerned that Osama bin Laden might have a “dirty bomb,” a low-tech but scary weapon combining conventional explosives and readily available nuclear waste to spread radioactive particles over a wide area. It could be delivered by truck or other conventional methods.

However, it was also reported that same day that Congress was cutting the budget of the Nunn-Lugar program, designed to prevent terrorists and others from getting their hands on nuclear weapons material that can be used to make such rudimentary devices.

Missile defense also torpedoed the summit between Presidents Bush and Putin of Russia last month, resulting in a serious setback to nuclear weapons control. The two leaders had been expected to announce deep cuts in their nuclear arsenals and a deal to allow missile defense testing without killing the ABM treaty.

Unfortunately, Mr. Bush and Putin held a love-in rather than substantive talks, in part because Bush was unwilling to give up the idea of quick deployment of missile defense and wanted a quick death for the ABM treaty. He also was loath to put any arms control agreement in writing.

Mr. Bush’s hard-line negotiating position ignored two facts: First, even under the rosiest scenario, no missile defense system will be ready before 2008 at the earliest.

Second, virtually all technical experts believe that the ABM treaty does not restrict the missile defense research and testing that the administration needs in the next several years.

Missile defense is a debate we do not need to have right now. We should keep testing while not basing our national security strategy on a pipe dream. But Washington’s most passionate debates often have a life of their own fueled by egos and politics, not sound policy or reality. So it is with missile defense.

Fortunately, the fallout from this weapon, so far, is only political.

Christopher Madison directs the missile defense project at the Council for a Livable World Education Fund.