Senate Democrats and Republicans scrambled yesterday to avoid a high-stakes confrontation over a treaty banning the testing of nuclear weapons, as both sides appeared increasingly convinced that they would be better off politically without a vote.

After delaying consideration of the Comprehensive Test Ban Treaty for more than two years, the Republican leadership surprised the White House last week by scheduling a quick vote on ratification for next Tuesday.

While Republicans clearly have enough votes to defeat the treaty, Senate Majority Leader Trent Lott (R-Miss.) started backing away yesterday, saying "the timing is not right" for a decision. But he also insisted he would only consider calling off the vote if the administration and Democrats agreed not to push for ratification until after next year's elections.

Democrats suggested that Republicans had been intimidated by a White House lobbying effort that portrayed defeat of the treaty as an invitation to proliferation of nuclear weapons in the Third World and the starting bell for a new arms race with Russia and China.

Some Democratic leaders, meanwhile, concluded that they would prefer to let the issue drop rather than face certain defeat in a vote next week.

President Clinton has considered the treaty a top legislative priority since he sent it to the Senate for ratification in 1997, but as yesterday's parliamentary maneuvering unfolded, the White House seemed increasingly resigned to the prospect that he will leave office without seeing it adopted.

Democrats were considering a Republican plan to put off a vote until after a new Congress and president are elected next year, although the minority had not agreed to it, according to Senate aides who said a decision on how to proceed could be made as early as today.

Late yesterday White House aides stopped short of saying they would insist on a vote if calls for a postponement grow louder. Asked whether he thought the Senate should delay action, Clinton said, "I'm going to work and do the best I can, and we'll see what happens."

The treaty, which Clinton signed in 1996, would ban all weapons tests that produce a nuclear chain reaction. In addition, it would establish an international monitoring system with more than 300 sensors to measure seismic activity and other indications of testing, and the treaty would allow for inspections of suspected test sites.

Although 154 nations have signed the treaty, only 47 have ratified it. China, Russia, India and Pakistan -- the nations that the Clinton administration is most concerned about -- have indicated that they are waiting for the United States to act before they consider ratification. So far, the treaty has been ratified by only 23 of the 44 nuclear-capable countries that must confirm it before it legally takes effect.

"It will end nuclear weapons testing forever, while allowing us to maintain our military strength in nuclear weapons and helping to keep other countries out of the nuclear weapons business," Clinton said yesterday at a Pentagon ceremony.

Even as opinion in the Senate shifted toward avoiding a confrontation, Republicans and Democrats jockeyed to see who would end up taking responsibility.

Lott insisted that Clinton and the Democrats would have to take the first step. "If they would indicate some willingness to let the next administration and the next Congress consider this and vote on it, we'd entertain that," he said.

Sen. Joseph R. Biden Jr. (Del.), the ranking Democrat on the Foreign Relations Committee, predicted that the vote would be canceled within the next 24 hours, with Democrats joining Republicans in postponing consideration of the treaty.

Ratification would require assent by two-thirds of the Senate. Republicans have the 34 votes to defeat the treaty but face the difficult choice of inviting political as well as international risk by voting against it, or defying their party leaders by voting for it. "It's a question of which poison they get to take -- arsenic or hemlock," Biden said.

He added that he did not believe any Republican would want to run next year having voted to "kill a treaty that said no one could explode nuclear weapons."

The administration argues that the treaty will inhibit the kind of full-scale nuclear testing that other countries need for development of new weapons or testing of their existing arsenals. The United States, on the other hand, has a $4.5 billion-a-year program for "stockpile stewardship" using superior technology that, according to the administration, ensures the reliability of U.S. weapons without testing.

In addition, the treaty contains provisions for inspections and monitoring that would improve the U.S. ability to detect and analyze foreign nuclear tests, according to administration officials.

Republicans have raised two major objections to the treaty. They argue that the U.S. inventory of nuclear weapons will deteriorate without adequate testing. With the CIA encountering technical difficulties gathering information on other countries' low-level nuclear tests, the Republicans also contend that the treaty is impossible to verify.

Sen. John F. Kerry (D-Mass.), a member of the Foreign Relations Committee, said Clinton had not formally requested that the vote be postponed. But, he added, "I think it would be the White House preference not to have a vote now."

In late afternoon, Lott and Minority Leader Thomas A. Daschle (D-S.D.) spoke on the Senate floor and agreed to start negotiations over a means to postpone the vote. As the Senate session ended yesterday evening, Lott returned to the floor to dispel rumors of an imminent deal. "Just calm down and relax," he told his colleagues, adding that for the time being the vote was still on, but that he and Daschle were discussing alternatives.

After his remarks on the floor, Lott told reporters that the vote would be held next week unless the administration agreed to forgo consideration of the treaty for the remainder of the 106th Congress, which lasts through the end of next year. "If we're going to vote on this issue in this Congress, it's going to be next Tuesday or Wednesday," he said.

Biden said that if the vote were postponed, Democrats will have accomplished "all they set out to do," including hearings, media attention and an "energized" president, which was not the case a couple of days ago. "The debate is engaged, and the Republicans are exposed, and we live to fight another day," he said.

Staff writer Charles Babbington contributed to this report.

A HISTORY OF NUCLEAR TESTS

Country:

Years:

Atmospheric tests

Underground tests

Totals:

U.S.

'45-'92

215

815

1,030

U.S.S.R.

'49-'90

219

496

715

FRANCE

'60-'96

50

160

210

U.K.

'52-'91

21

24

45

CHINA

'64-'96

23

22

45

INDIA

'74-'98

0

3

3

PAKISTAN

'98-'98

0

2

2

Pakistan and India conducted nuclear tests in 1998, the most recent known. Neither has signed the nuclear test ban treaty.

SOURCE: Physicians for Social Responsibility