It is a concept so fantastic that it was ridiculed when President Reagan first brought it to the nation's attention on March 23, 1983.
In an otherwise ordinary speech, Mr. Reagan called on America's scientists to develop a defense system that could "intercept and destroy strategic ballistic missiles before they reached our own soil or that of our allies."
Seventeen years later, Reagan's "star wars" plan has evolved into National Missile Defense (NMD), but it is only slightly less contentious. Moving forward with a system could dramatically alter America's strategic relationship with the rest of the world, and even trigger a new arms race. Abandoning the project, however, could show vulnerability in the world's only superpower.
President Clinton becomes eligible this summer to either delay or deploy a limited system. The administration says it will base a decision on four factors: technology, outside threat, price, and national-security concerns, including arms control.
Few doubt, however, that a fifth factor is at play: politics. Successful handling of the NMD issue by Mr. Clinton would be a legacy-builder and a boost for presidential candidate Al Gore.
The Republican leadership, on the other hand, is increasingly leaning toward postponing a decision - in the hope that George W. Bush will win the White House and implement a more comprehensive version of the system.
How serious is the 'rogue' threat?
One of the biggest rationales for moving ahead with NMD has been the technological advances made by potential enemies of the US. Leading the charge has been North Korea, which is thought to be selling the technology to other countries with questionable intent.
By some estimates, North Korea could gain the ability to reach the Pacific US with a ballistic missile by 2005. Because of that, US officials are under great pressure to build a NMD before then. To do so, Pentagon officials say they would have to break ground on an interceptor base as soon as possible.
US officials are not only suspicious about North Korea's latest missile developments. They are also worried about what the warheads could carry. Pyongyang has a nuclear program (suspended in 1994) and possibly chemical- and biological-weapons programs. NMD skeptics say the North Korean threat is overblown, partially to justify more defense spending. North Korea is so poor it can barely feed its people, and recent satellite photos indicate its missile facility is unimpressive.
Other countries, such as Iran, Iraq, and Libya, are not as advanced as North Korea and are not thought likely to pose such an early threat. Russia and China have the ability to reach the US, but officials say the NMD would not have the capacity to protect against their large and advanced nuclear arsenals - unless they launched a missile by mistake.
Analysts say NMD is akin to hitting one speeding bullet with another. Even Pentagon officials admit they have their hands full. NMD works first with linked radar systems, on ground and in space, that track an incoming ballistic missile. As the enemy projectile approaches, the US fires a defensive missile toward an estimated point of impact. The defensive missile then releases a "kill vehicle," which hones in on the enemy warhead.
Under the proposed first phase of NMD, the US would have 100 interceptor missiles in Alaska. In theory, they could protect all 50 states against a limited attack from a "rogue state" in Asia like North Korea. The idea is to phase in more interceptors in more locations, to protect against attack from Iran or Iraq.
The Pentagon has conducted two tests so far, firing one missile at another. One worked and one failed. A crucial third test is in June.
Perhaps the greatest technological challenge is distinguishing the real enemy warhead from decoys. NMD opponents argue that if a country had the technology to hurl a nuclear weapon halfway around the world, it surely could confuse America's kill vehicle. Pentagon officials say the kill-vehicle sensors and technology are improving.
For US, diplomatic complications
NMD opponents have focused their efforts on what they say are the detrimental international-security implications. Missile defense is opposed by almost every country in the world, including China, Russia, and European allies of the US.
Even a limited system would violate the 1972 Antiballistic Missile Treaty with the Soviet Union. The ABM treaty was devised with the assumption that both the US and USSR could destroy each other. If that mutual deterrence were thrown out of balance, the logic goes, there would be a greater likelihood of an attack or a new arms race.
The Clinton administration is trying to convince the Russians to change the ABM treaty, arguing that the proposed US system is not designed to match their overwhelming threat. But Moscow has resisted, fearing the system could expand to include thousands of interceptors, upsetting the nuclear balance.
Perhaps more concerned is China, which relies on a small arsenal of ICBMs for deterrence. The Chinese say they cannot understand why a power like the US would be so afraid of North Korea. In their eyes, Beijing is the target of the US plan.
The Europeans oppose NMD on grounds it will alter the balance of risk they share with the US. They could become proxy targets of rogue states (most of which are closer to them than to the US).
Finally, Russian President-elect Vladimir Putin has linked other arms-control treaties to the ABM treaty. Nonproliferation advocates fear that the US will withdraw from the ABM treaty, and the rest of the accords will fall like a house of cards. Yet, supporters of NMD argue, those treaties were products of the cold war, and today the US faces an entirely different threat.
NMD is expensive, especially considering that defense spending has dropped from its cold-war highs. Yet some say the benefits could outweigh almost any cost. The US has already spent about $60 billion on missile defenses, dating from Reagan's first plan. Today the level of spending is about $4 billion per year. The Pentagon has not put a price tag on a completed system, but says the first phase, with 100 interceptors, would cost $25.6 billion. The Congressional Budget Office estimates the first phase at $29.5 billion and the entire system at $60 billion over the next 15 years.
(c) Copyright 2000. The Christian Science Publishing Society