The administration and its Senate allies, including Byron Dorgan, ["A Vote for a Safer World," op-ed, Oct. 4] laud the Comprehensive Test Ban Treaty's (CTBT) ban on all explosive nuclear testing as a step toward a nuclear-free world. But anyone who looks past the sound bites will realize that this pact flunks the first test of arms control -- it will not make us safer.

We are told that a test ban will stop countries from acquiring nuclear weapons. But those who threaten us the most (North Korea, Iran and Iraq) already have violated the 1968 Nuclear Nonproliferation Treaty by pursuing a nuclear capability. Do treaty proponents expect us to believe that the CTBT will keep countries from testing weapons they promised not to develop in the first place?

What if countries want to test anyway? We may never know. Low-yield tests can be useful to bomb-builders but can't reliably be detected. Larger tests can be muffled by placing the bomb in an underground cavity or masking it with a conventional mining explosion. To verify compliance with the treaty, we would have to count on a country to violate it openly, or on the goodwill (through its willingness to permit inspections) of a country with something to hide.

Banning testing and stopping the spread of nuclear weapons are two different things. One reality of nuclear weapons is that simple yet strategically significant bombs don't need testing at all. America put an end to World War II with a bomb that had never been tested. For years, we have conducted our international affairs with the assumption that Israel and North Korea have a nuclear capability, even though we have never been certain that they have tested their designs.

When it comes to our adversaries, the treaty does us no good. When it comes to our own deterrent, the treaty does real harm. Sen. Dorgan asserts that the treaty "will allow the U.S. to retain a safe and reliable nuclear deterrent." But prohibiting -- absolutely and permanently -- even low-yield, underground testing of our own weapons denies us the only proven and fail-safe means of knowing if our weapons work, if they pose a safety hazard and if a remedy has actually solved a problem.

We must know that our weapons will work. To be deterred, our adversaries must know it too. Despite our technical skill, one-third of all new weapon designs since 1958 have later required nuclear tests to fix problems. President Bush noted in a report to Congress in January 1993: "Of all U.S. nuclear weapons designs fielded since 1958, approximately one-third have required nuclear testing to resolve problems arising after deployment."

In place of testing, the administration proposes a set of research projects called the Stockpile Stewardship Program, which would use computer calculations based on existing test data to predict changes in the safety and reliability of our weapons. The program may one day be a useful diagnostic tool. But by all accounts, it will take another decade to mature. Even then, it can never provide the same level of certainty as testing. (Mr. Goodwrench can use all the computers he wants to help fix my car, but I expect him to actually test drive it before giving me back the keys!)

The United States may never be able to stop North Korea, Iraq, Iran or any other nation from having nuclear weapons. But our own deterrent has been a source of security and stability for 50 years. We have a flawless safety record. Our nuclear umbrella reassures our allies and keeps them from acquiring their own bombs. This treaty's only certain effect will be to increase doubts -- among our allies, our enemies and our own leaders -- about our weapons. Whatever one thinks of nuclear weapons, we can all agree that uncertainty about them can only be destabilizing.

The flaws in this treaty are as clear as they are inescapable: The CTBT won't prevent nuclear weapons from getting into the wrong hands. It won't allow us to verify whether or not rogue states are testing. And it gradually will erode confidence in our own deterrent. In sum, we will not be safer. The Senate should reject the CTBT.

The writer, a Republican senator from Arizona, is a member of the Intelligence Committee.