For more than five decades, we have served in a variety of foreign policy, national security and intelligence positions for both Republican and Democratic administrations. A common thread in our experience is that our national interest is best served when America leads. When America hesitates, opportunities to improve our security are lost, and our strategic position suffers. This year, America has an opportunity to lead a global effort to strengthen nuclear nonproliferation by ratifying the Comprehensive Test Ban Treaty (CTBT).

This fall, a review conference will meet to discuss ways to bring the CTBT into effect even if it has not been approved by all 44 nuclear-capable nations (i.e., those states with nuclear reactors for research or power). The United States was the first nation to sign the CTBT in September 1996; 151 nations have now followed that lead. The U.S. Senate, however, has refused to consider ratification of the treaty, and only those nations that have ratified it will have a seat at this fall's conference. Approval of the CTBT by the Senate is essential in order for the United States to be in the strongest possible position to press for the early enforcement of this vital agreement. Failure to act will undercut our diplomatic efforts to combat the threat from the proliferation of nuclear weapons.

The president rightly has referred to the CTBT as the "longest-sought, hardest-fought prize in the history of arms control." President Eisenhower was the first American leader to pursue a ban on nuclear testing as a means to curb the nuclear arms race. Today, such a ban would constrain advanced and not-so-advanced nuclear weapons states from developing more sophisticated and dangerous nuclear weapons capabilities.

This is particularly important in South Asia. Last year, both India and Pakistan conducted nuclear tests, threatening a dangerous escalation of their nuclear arms competition. Both countries now have expressed a commitment to adhere to the CTBT this year. U.S. ratification would remove any excuse for inaction on the part of these nations and would strengthen their resolve.

The CTBT also fulfills a commitment made by the nuclear powers in gaining the agreement of 185 nations to extend indefinitely the Nuclear Nonproliferation Treaty in 1995. The NPT remains the cornerstone of the worldwide effort to limit the spread of nuclear weapons and reduce nuclear danger.

We strongly embrace President Reagan's vision of a world free of nuclear weapons. The administration needs to engage Russia on deep reductions in nuclear forces, despite the disruption in our bilateral relations resulting from the crisis in the Balkans. In the meantime, the United States will be able to maintain the safety and reliability of its own stockpile through the Department of Energy's science-based stockpile stewardship program. Our confidence in this program underpins our judgment that there is no technical reason why the CTBT is not the right thing to do.

President Reagan's maxim -- trust but verify -- is still true today. With the CTBT, the United States will gain new tools to assess compliance with a ban on nuclear testing -- including the right to request a short-notice, on-site inspection if we had evidence that a test might have occurred. Combined with the treaty's extensive international monitoring regime and our own intelligence resources, the CTBT is effectively verifiable.

The Senate has an obligation to review expeditiously major treaties and agreements entered into by the Executive so that the world can be sure of America's course. When President Reagan signed the INF Treaty in December 1987, which eliminated an entire class of missiles, hearings in the Senate Foreign Relations Committee began within weeks, and the Senate voted to approve the a treaty within six months. In comparison, the CTBT was signed by President Clinton more than 2 1/2 years ago but still awaits its first hearing.

In May 1961, President Eisenhower said that not achieving a nuclear test ban "would have to be classed as the greatest disappointment of any administration -- of any decade -- of any time and of any party." Similarly, failure to ratify the CTBT would have to be regarded as the greatest disappointment of any Senate, of any time, of any party. We urge the Senate to ratify the CTBT now.

Paul H. Nitze is a former arms control negotiator and was an ambassador-at-large in the Reagan administration. Sidney D. Drell is an adviser to the federal government on national security issues.