President Clinton led a Democratic effort yesterday to turn a stinging policy defeat into a political advantage, vowing to keep fighting for the nuclear test ban treaty soundly rejected by the Senate and warning that voters may view Republican leaders as out of step with national priorities.

At an hour-long White House news conference, Clinton said his administration will continue to refrain from testing nuclear weapons, and he predicted the United States eventually will ratify the pact. But he also warned that if an anti-treaty president is elected, Russia, China, Pakistan and India will renew testing of nuclear bombs.

Texas Gov. George W. Bush and the other Republican presidential hopefuls have said they oppose the Comprehensive Test Ban Treaty, which the GOP-controlled Senate rejected Wednesday night mostly along party lines.

Despite their vote against the treaty, many Republican senators said yesterday they do not want the United States to resume nuclear testing.

Vice President Gore and other Democrats signaled they will try to turn the rejection of the treaty against GOP candidates next year, portraying them as isolationists and captives of a hard-right contingent that threw away a chance to promote a safer world.

"This vote goes against the tide of history," Gore said in the first television ads of his presidential campaign, to air this week in Iowa, New Hampshire and nationally on CNN. Gore and Democratic rival Bill Bradley said that, if elected president, they would resubmit the treaty to the Senate.

Senate Minority Leader Thomas A. Daschle (D-S.D.) said: "We expect that this should be and will be a national issue next year in the presidential elections."

During the Senate's consideration of the test ban treaty, Clinton had said it should be decided on substantive, not political, grounds. Yesterday, however, the issue appeared almost completely politicized, as Clinton devoted much of his news conference to attacking Republicans for rejecting the pact.

"Hard-line Republicans irresponsibly forced a vote against the . . . treaty," Clinton said, calling it "partisan politics of the worst kind." He acknowledged that nuclear disarmament is hardly a hot topic for most Americans, but warned that voters in the 2000 elections may take issue with the GOP's priorities.

"I did not expect that this would ever be such a big issue," the president said. "I think it might be now."

Republicans disputed Clinton's claims, saying they rejected the treaty for valid, nonpolitical reasons.

"Some of the most thoughtful senators that ever served in this body" agreed that compliance by other nations could not be adequately verified, Senate Majority Leader Trent Lott (R-Miss.) told reporters after the president's news conference. "This was a flawed treaty."

To bolster their claim of political motives by the GOP, Democrats cited a comment by Sen. Jesse Helms (R-N.C.) during Wednesday night's Senate debate. Helms, chairman of the Foreign Relations Committee, suggested that British Prime Minister Tony Blair might end a treaty-related phone call to Clinton by saying, "Give Monica my regards." He was referring to Monica S. Lewinsky, the White House intern whose liaison with Clinton prompted his 1998 impeachment.

Asked yesterday if such remarks suggested that Republicans used the treaty issue as a vendetta, Clinton replied: "It has been my experience that very often in politics when a person is taking a position that he simply cannot defend, the only defense is to attack the opponent. And that's what I took it as, a form of flattery."

Clinton, who appeared relaxed and occasionally joked with reporters, showed similar equanimity when asked why he hasn't denied that he "intentionally lied" in his deposition in Paula Jones's sexual harassment lawsuit. "When I am out of office, I will have a lot to say about this," Clinton said evenly. "Until then, I'm going to honor my commitment to all of you to go back to work."

The president also used the news conference to rebuke congressional Republicans for failing to enact all the appropriations bills to finance the federal government in the fiscal year that began Oct. 1. Clinton and Congress agreed to a three-week extension, but lawmakers concede that further postponements, or "continuing resolutions," will be needed.

"When I signed the continuing resolution two weeks ago, I urged Congress to roll up its sleeves and finish the job the American people sent them here to do," Clinton said. "I said they should stop playing politics, stop playing games, start making the necessary tough choices. Instead, we had the Republicans lurching from one unworkable idea to the next." He accused GOP leaders of using "budget gimmicks to disguise the fact that they are spending the Social Security surplus."

House Majority Leader Richard K. Armey (R-Tex.) denied that GOP spending plans would "spend one penny of Social Security." He also said Clinton's proposal to raise cigarette taxes "would fall most heavily on low-income Americans." Clinton said yesterday, "we know that raising the price of a pack of cigarettes is one of the best ways" to discourage teenage smoking.

On another topic, Clinton declined to echo Gore's portrayal of Bradley as a disloyal Democrat. But he praised Gore's performance as vice president. "I expect him to win," he said. "But I expect to support the nominee of my party, as I always have. And I think that I can serve no useful function by talking about anything other than issues."

Even though the test ban treaty fell far short of the two-thirds Senate majority needed for ratification, Clinton said, his administration "will not abandon the commitments inherent in the treaty and resume testing ourselves. I will not let yesterday's partisanship stand as our final word on the test ban treaty."

"I call on Russia, China, Britain, France and all other countries to continue to refrain from testing," he said, referring to the world's other major nuclear powers. "I call on nations that have not done so, to sign and ratify the Comprehensive Test Ban Treaty. . . . When all is said and done, I have no doubt that the United States will ratify this treaty."

In a thinly veiled reference to the Republican presidential contenders, Clinton said: "Now, if we ever get a president that's against the test ban treaty, which we may get -- I mean, there are plenty of people out there who say they're against it -- then I think you might as well get ready for it. You'll have Russia testing, you'll have China testing, you'll have India testing, you'll have Pakistan testing. You'll have countries abandoning the Non-Proliferation Treaty."

Clinton rejected complaints that he and his staff didn't work hard enough to build Senate support for the treaty before Lott surprised them last month by scheduling a vote. "If we would have had a normal process, you would have seen a much more extensive public campaign," he said. "There was simply no time to put it together. But I talked about this over and over and over again in many different contexts, and I think that given the time we had, we did the best we could."