Regardless of the outcome, the military's attempt to shoot down an intercontinental missile high over the Pacific this weekend is sure to intensify the fierce political debate over President Bush's missile-shield plans. 

The test comes at a sensitive time as Bush heads for Europe and meetings with allies who oppose the program. 

Trying to lower expectations, Pentagon officials suggested that a miss in Saturday night's test would still yield useful information. The administration plans to proceed no matter how the test turns out. 

It will be the fourth attempt to shoot down a long-range missile with a prototype interceptor. Two previous tests failed and one was successful. 

Missile defense advocates say individual tests at this stage are not that significant, given the technological complexities of a concept likened to stopping a bullet with another bullet. 

But the administration and its congressional allies can be expected to seize on a successful interception to press for an accelerated testing schedule and to step up criticism of the 1972 Anti-Ballistic Missile Treaty. 

Likewise, detractors will depict a failure as one more reason to scrap the project. A miss would complicate the administration's efforts to persuade Congress to spend $8.3 billion for missile defense research and testing in 2002, a nearly 60 percent increase over this year. 

"I think we have to rethink our priorities here," said Sen. Max Cleland, D-Ga. "I can find no good reason to justify the increase." 

Bush leaves for Europe on Wednesday. In Italy, he will join leaders of Japan, France, Germany, Britain, Canada, Italy and Russia for an annual summit of industrial democracies. 

On a visit to Europe last month, Bush found allies wary of his plan. 

German and French leaders openly worried about triggering a new arms race. Russian President Vladimir Putin suggested American defiance of the ABM treaty could prompt Russia to put more nuclear warheads on its missiles. 

The treaty bars both the United States and Russia from deploying a national missile-defense system. The theory was that such an explicit ban would discourage both sides from launching the first strike out of fear of retaliation. Bush has said the treaty is a relic of the Cold War and should be left behind. 

Defense Secretary Donald Rumsfeld cautioned against reading too much into this latest test flight. Sen. John Warner of Virginia, senior Republican on the Senate Armed Services Committee, called it "just another building block. Each set of results stand on their own." 

The committee's new chairman, Sen. Carl Levin, D-Mich., essentially agreed. "Each test is not in and of itself determinative of where this program goes," he said. 

But Levin said his main concern is that the ABM treaty might soon be violated. "It could unleash an arms race and a very negative response from either Russia or China," he suggested. 

The Pentagon will begin groundbreaking for a new missile defense test range in Alaska as early as August. Defense officials say some segments could be deployed as an interim defense if necessary, even before they are fully tested. 

Democratic leaders argue against spending billions more on a system that may not work and would violate a landmark treaty. But Condoleezza Rice, Bush's national security adviser, suggests they're trying to have it both ways. 

"We're in a Catch 22 and a circular argument," Rice told reporters. "People say, `You can't demonstrate that this system is going to work.' Well, that's right, because there are so many testing limitations on such a system that you can't demonstrate if it's going to work." 

Democratic pollster Mark Mellman, who has done work for missile-shield opponents, said several recent surveys show missile defense to be "an extraordinarily low priority for people." But this lack of interest "turns to opposition" when the subject of failed tests and treaty violations is raised, he said. 

Republican politicians have long argued that many Americans believe — incorrectly — that the nation's cities are protected already by some vague sort of missile defense system. 

Mellman said his polling, too, has found such erroneous assumptions to be widespread. 

That being the case, he quipped, "Why pay for it again?"