The GOP-controlled Senate emphatically rejected the Comprehensive Test Ban Treaty yesterday, dealing a devastating blow to a pact that has been at the center of global efforts to curb the spread of nuclear weapons.

Senate Republicans said it would be impossible to ensure that other nations were abiding by the treaty, and they argued that the pact would make it difficult for the United States to ensure the viability of its own nuclear stockpile. They rejected Democratic complaints that they were sending a dangerous message to other nations interested in joining the nuclear club.

Indeed, the 51 to 48 vote against the pact fell largely along party lines, with only four Republicans joining 44 Democrats in supporting the treaty -- far short of the two-thirds necessary for ratification.

The vote was President Clinton's biggest foreign policy defeat on Capitol Hill and represented another collapse of bipartisanship in a Congress characterized by a high degree of strife and paralysis. It also could have far-reaching international repercussions. Major U.S. allies including Britain, Germany and France have warned that rejection of the test ban treaty would raise serious doubts about America's commitment to reducing the nuclear arms threat.

Declaring that "the fight is far from over," Clinton last night denounced the treaty's rejection as "reckless" and "partisan."

"For now the Senate has said no, but I am sending a different message. We want to limit the nuclear threat. We want to bring the test ban treaty into force," Clinton said on the White House lawn.

"When all is said and done, the United States will ratify the treaty," he said.

"This is a terrible, terrible mistake," said Minority Leader Thomas A. Daschle (D-S.D.). "If politics don't stop at the water's edge, nothing does."

Foreign Relations Committee Chairman Jesse Helms (R-N.C.) said the only terrible thing was the treaty itself. It is "the most egregious treaty ever submitted to the Senate for advice and consent . . . a dangerous treaty" that merits rejection, he said.

Democrats vowed to keep up pressure for ratification and predicted that the Senate's vote will become an issue in next year's elections. The treaty could be brought up again in the 107th Congress if the next president decides to resubmit it.

But in the meantime the vote made history: Not since the Treaty of Versailles to establish the League of Nations after World War I had the Senate formally rejected a major arms control accord, although it has often delayed action to avert defeat and has occasionally rejected treaties on other subjects. The Senate last rejected a treaty in 1983, when it turned down an agreement dealing with aviation rules.

In yesterday's vote, all Republicans voted against the treaty except for four moderates -- John H. Chafee (R.I.), James M. Jeffords (Vt.), Gordon Smith (Ore.) and Arlen Specter (Pa.) -- who joined 44 of 45 Democrats in voting for it. Sen. Robert C. Byrd (D-W.Va.) voted "present" because he wanted the vote delayed so he could resolve reservations he has about the pact. Among Washington area senators, only John W. Warner (R-Va.) voted against the treaty.

The treaty technically remains before the Senate but cannot be brought up again except by Majority Leader Trent Lott (R-Miss.), who is adamantly opposed to further consideration of the pact in this Congress. At the end of next year, it would go back to the Foreign Relations Committee.

Rejection of the treaty had been expected, but for a time it appeared that the vote might be put off indefinitely. As the vote approached, senior lawmakers of both parties struggled to find a face-saving way to delay it, arguing that rejection could trigger a new round of testing by emerging nuclear powers. By yesterday, 62 senators had signed a letter urging delay. But the effort collapsed when a small group of GOP conservatives, including Helms, insisted on concessions that the White House and Senate Democrats were unwilling to give.

"There's a limit to what I can do. . . . I've reached that limit," Daschle said at a news conference. More resigned than angry, Daschle blamed "a small group of senators on the far right" for scuttling a tentative deal that he reached Tuesday with Lott to delay the vote.

As some saw it, the vote resulted in large part from 6 1/2 years of bad relations between Clinton and congressional Republicans that culminated last winter with the president's impeachment and trial. "The White House and Congress just don't trust each other at all," said Marshall Wittmann, congressional analyst at the Heritage Foundation. "This is a Cold War that will not end until there is another president."

Whether the treaty ultimately will be passed could hinge on the 2000 elections. Vice President Gore and Bill Bradley support the treaty, but Republican front-runner George W. Bush opposes it while supporting the current testing moratorium. Bush has said compliance cannot be verified, the treaty will not keep other countries from testing and it will restrict the United States' ability to test safely in the future.

The treaty, which Clinton was the first international leader to sign in 1996, seeks to stop all nuclear tests by countries that sign it, extending an earlier ban on atmospheric explosions to those that are conducted underground. It also would set up procedures for monitoring compliance and imposing sanctions on violators.

Proponents, mainly Democrats, argued that, with the United States having abandoned testing in 1992, the treaty would lock in U.S. nuclear superiority and deter the spread of nuclear weapons by making it more difficult to test them.

Opponents, mostly conservative Republicans, contended that compliance by other countries could not be verified and that the technology for alternatives to testing by explosion was not advanced enough to ensure the safety and viability of the U.S. nuclear stockpile.

The treaty has been signed by 154 countries, but only 51 have ratified it. To be implemented, it must be ratified by all 44 countries with varying degrees of capability to produce nuclear weapons, and only 26 have done so. Of the five declared nuclear powers, Britain and France have ratified the treaty, while Russia, China and the United States have not. Treaty proponents have said some countries are unlikely to ratify the treaty until the United States does so.

Clinton submitted the treaty two years ago. It languished in the Foreign Relations Committee until three weeks ago, when Lott, nettled by charges of foot-dragging by Democrats, decided to schedule an immediate vote. He did so in full confidence that Republicans had more than enough votes to defeat the treaty. Even Democrats conceded that point, arguing that they only wanted hearings on the issue to help build public pressure for ratification.

But as the vote neared, pressure for a delay mounted, especially from Democrats and internationalist Republicans such as Warner, chairman of the Armed Services Committee. In response to Republican demands, Clinton asked for a delay, first orally, then in writing. But ultimately, efforts to delay the vote failed.

Samuel R. "Sandy" Berger, the president's national security adviser, said that the administration will continue to check U.S. nuclear weapons with laboratory tests and computer simulations rather than explosions, and that it will continue working for other arms agreements.

"We're not going to throttle back on the business of controlling nuclear weapons in a safe way," he said.

He also left open the possibility that Clinton will push for ratification next year.

Key Treaties On Arms Control

Chemical Weapons (1997): President Clinton went all-out to win Senate ratification of the Chemical Weapons Treaty in April 1997. The Senate approved it 74 to 26. It prohibits the manufacture, stockpile and use of chemical weapons.

START II (1996): The Strategic Arms Reduction Treaty was ratified by the Senate in 1996 and would halve the U.S. and Russian nuclear arsenals to between 3,000 and 3,500 warheads each. Russia's parliament has yet to ratify it.

START I (1992): President Ronald Reagan's negotiations with the Soviet Union to reduce strategic nuclear warheads on both sides evolved into the START I treaty, signed in 1991 and ratified the next year on a 93 to 6 Senate vote.

INF Treaty (1988): The Senate voted 93 to 5 in May 1988 for a U.S.-Soviet treaty banning intermediate-range nuclear force missiles, leading to the destruction of an entire class of nuclear weapons.

Anti-Ballistic Missile Treaty (1972): The ABM Treaty, which limits the scope of anti-missile systems, was an outgrowth of the first round of strategic arms limitation talks. It was presented to the Senate by President Richard M. Nixon and ratified 88 to 2 in August 1972.

Nuclear Nonproliferation Treaty (1969): The treaty banning the spread of nuclear weapons to nations that did not already possess them was sent to the Senate by President Lyndon B. Johnson in 1968 and ratified in March 1969, after Nixon took office. The vote was 83 to 15.