WASHINGTON -- President Clinton announced yesterday a ban on all U.S. nuclear testing, ending a long-running debate inside the administration and boosting the prospects for drafting a worldwide, comprehensive test ban treaty.
"This is an historic milestone in our efforts to reduce the nuclear threat, to build a safer world," said Mr. Clinton, rejecting both the Pentagon's initial advice and Republican demands to allow low-yield tests to check the reliability of the nation's nuclear arsenal.
"A comprehensive test ban is the right step as we continue pulling back from the nuclear precipice, a precipice which we began to live with 50 years ago this week," said Mr. Clinton, referring to the nuclear devastation of the Japanese cities of Hiroshima and Nagasaki.
Mr. Clinton said annual scientific tests -- not underground explosions -- will be used to ensure the safety of the nuclear stockpile. But he reserved the right, if problems develop, to cite the "supreme national interest" and order -- in consultation with Congress -- any needed testing.
Within the administration, Mr. Clinton faced initial pressure to permit limited tests from Defense Secretary William J. Perry, the Joint Chiefs of Staff, CIA Director John M. Deutch, a pro-test faction on the National Security Council staff, and scientists who manage the nuclear weapons program.
But by the time Mr. Clinton announced his decision yesterday, he had the unanimous support of all the national security agencies, according to Robert Bell, special White House assistant for defense policy.
"It's not a case of someone being overruled or one side winning out over the other in an internal debate," Mr. Bell said.
Another official familiar with the internal debate said the military leaders had wanted guarantees that the nuclear weapons were reliable, and the scientific community, which would have to repair any flawed weapons, wanted the opportunity to confirm the results of laboratory experiments with actual tests.
Their insistence on testing was overcome, according to the official, "by our ability to make it clear that the safety and reliability of the stockpile could be adequately addressed in other ways," and by the president reserving the right to test in emergencies.
"The feeling is that we can proceed with this with a lot of confidence," said Pentagon spokesman Kenneth Bacon.
But some Republican members of Congress remained unpersuaded.
"I remain to be convinced that we can monitor the reliability, safety and accuracy of our nuclear weapons without the ability to test them," said South Carolina Sen. Strom Thurmond, Republican chairman of the Senate Armed Services Committee. But Congress does not have authority to overrule the president's policy.
The U.S. position improves the prospects of reaching an international comprehensive test ban treaty at the Geneva Disarmament Conference by the deadline of autumn, 1996, said John D. Holum, director of the U.S. Arms Control and Disarmament Agency.
The search for agreement in Geneva has been stymied by uncertainty over whether the Clinton administration would accept an outright ban or reserve the right to routinely conduct small tests.
"The U.S. position was like being 'a little bit pregnant,' " said Bob Gaskin of Business Executives for National Security. "Either you are testing or you are not. This is a courageous step by the president. It really puts us in a position of leadership."
The decision came 24 hours after France announced that it would support a total ban -- but only after completing a series of nuclear test blasts in the South Pacific between September and May.
The French test plans have caused an international furor in Japan, Australia and other Pacific nations. It was in an effort to quell the uproar that France agreed to the test ban.
The three other nuclear powers and their positions in the test ban negotiations are:
* Russia. The government of President Boris N. Yeltsin has insisted on the right to continue medium-yield testing, leaving what Mr. Bell called "a major point of negotiation."
* China. Beijing wants the right to conduct "peaceful" nuclear tests, but has said it would accept a ban once the other nuclear powers have reached agreement.
* Britain. Without a test site of its own, Britain used the U.S. facility in Nevada, which will be covered by the Clinton administration's ban.
Even if agreement is eventually reached in Geneva, a global treaty would require ratification by a two-thirds majority of the Senate. Last week the GOP-controlled chamber voted 56-44 to spend $50 million in fiscal 1996 on small nuclear tests, although none are planned.
"I don't think this administration is going to get anywhere near the 67 votes it would need," said Baker Spring, analyst with the conservative Heritage Foundation and a critic of banning tests.