The ultimate terrorist weapon is not anthrax, commercial airplanes used as weapons of mass destruction or even smallpox.

The deadliest terrorist threat is ballistic missiles carrying nuclear, chemical, or biological weapons aimed at American cities, and Americans "ain’t seen nothing yet" in the terrorist war unless our country develops protection against the ultimate terrorist weapon.

While we’re rightly gearing up protection against secondary but still scary terrorist threats, we remain totally defenseless against the most devastating weapon of them all.

It has been nearly 18 years since President Reagan first proposed missile defense – his "SDI" or Strategic Defense Initiative – yet successive administrations of both parties have done too little to make missile defense a reality. As we all know now in the post Sept. 11 world, we’re awfully late in having the necessary defenses in place to cope with the threats of the post-Cold War world.

Fortunately this sad state of affairs is now changing and fast. President Bush, showing real leadership and foresight, preaches how missile defense is essential to winning America’s war against terrorism. He tirelessly pushes to abandon the Cold War relic that ties America’s hands: the ABM (Anti-Ballistic Missile) Treaty.

Last weekend in Shanghai, China, the president made real progress toward dismantling the ABM with Russian President Vladmir Putin, who has come to realize that a new relationship with America is in Russia’s national interest because Russia also faces threats from terrorists and an Islamic world in turmoil.

The outline of the coming American-Russian strategic deal, to be consummated next month in the Crawford, Texas summit, is becoming crystal clear. In exchange for Russian willingness to scrap the ABM Treaty – or at least, to modify it so substantially as to allow deployment of missile defenses – the U.S. will agree to substantial reductions in strategic weapons.

Unilaterally cutting our vast strategic nuclear stockpile is long overdue. We can now go far below the 7,000 weapons in our current arsenal. We can even reduce our stockpile substantially below the 3,500 proposed some years ago in the formal arms negotiations.

President Bush can also offer Putin the sweetener of the United States using the technology in air defenses, metallurgy, and point defense Russia has developed over the past 30 years. This sweetener would furnish productive employment to top Russian scientists and much-needed money to Russian government coffers.

The critical measure of the deal’s success will be whether the U.S. can deploy, and not just research, missile defense. If so, then modifications in the ABM Treaty can be accepted. If not, then scrapping the treaty will be necessary.

Contrary to popular beliefs, such action does not entail breaking an international treaty. The ABM accord itself allows either side to abandon the treaty for "supreme national interests" in a changed security environment. If Sept. 11 doesn’t constitute such a change, nothing does. And if defending our country, our friends and our allies around the world does not constitute a "supreme national interest," again nothing does.

Once Russia agrees to modify or abandon the ABM, the Bush administration’s next challenge will be to persuade the liberal arms control community led by Sen. Joseph Biden, chairman of the Senate Foreign Relations Committee and Sen. Carl Levin of the Armed Services Committee. Even after Sept. 11, these opponents have remained in a Cold War time warp, arguing vigorously against any deployment of U.S. missile defenses.

Missile defense opponents were right when they pointed out that our foes can use other terrorism methods to attack us—in the case of Sept. 11, turning American airliners into guided missiles. But they were wrong when they said America's current foes couldn't match the degree of evil of Hitler, Stalin, or Mao Tse-Tung. Sept. 11 showed what evil rogue leaders can do.

Next time it could be actual missiles falling on American or European cities. Imagine how much easier it would be for America's attackers to buy a long-range missile or two from North Korea or Iraq, arm it with nuclear or chemical weapons and fire it at America's still defenseless shores.

Why make it easy for America's enemies? Why not shield America and its allies from one of the easiest means of inflicting the greatest horror?

Since Sept. 11 America has stood united and there has been no one to blame but the assailants. But that won't necessarily be true in the future if a vigorous missile defense program is not proposed and the beginning stages implemented by Thanksgiving.

If not, Americans in future years will say that more could have done to protect the nation. That would be an even greater tragedy than the one we're living through now.

Kenneth Adelman is a frequent guest commentator on Fox News, was assistant to U.S. Defense Secretary Donald Rumsfeld from 1975 to 1977 and, under President Ronald Reagan, U.N. ambassador and arms-control director. Mr. Adelman is now co-host of TechCentralStation.com.

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