"This is bigger than party politics. This is bigger than personal politics," Mr. Clinton told reporters before leaving for New York City for a fund-raising event. "This is about America's future."
The treaty Â— if ratified Â— would extend the present international ban on nuclear tests in the atmosphere to underground testing as well, resulting in a total ban on all nuclear explosions, no matter how small.
However, with virtually no Republican support, the treaty appeared headed to defeat in the Senate. Its ratification requires 67 votes in the GOP-led chamber if all 100 senators vote.
The president sent a personal message to the Senate, asking lawmakers to set aside whatever political commitments they may have made and consider "the implications of the treaty for our children's future."
He again held out the possibility that a vote, now scheduled for Tuesday in the Senate, could be postponed.
"All I ask is that we do what's in the national interest. Let's do the right thing for America," the president continued. "We cannot get caught up in a debate that would be unworthy of the children and grandchildren of Democrats and Republicans."
Senate Majority Leader Trent Lott, R-Miss., forced the issue by scheduling a quick vote on the treaty after Republicans had blocked it for two years.
The president's spokesman said Senator Jesse Helms, R-N.C., and other conservatives pushing for the quick vote are putting partisanship ahead of national interests, reports CBS News Correspondent Peter Maer.
The White House has rejected their demand that the president put in writing any request to delay a vote on an international nuclear test ban treaty.
The conservatives also want Clinton to promise Â— in writing Â— not to seek to revive the treaty during the 2000 presidential election year, a condition the White House has also rejected.
Defense Secretary William Cohen declared Wednesday that formal rejection of the treaty could speed the spread of nuclear weapons.
Energy Secretary Bill Richardson testified that rejection of the treaty "would announce that the United States refuses to lead on this issue."
The treaty is nothing less than a centerpiece of President Clinton's foreign policy legacy, CBS News White House Correspondent John Roberts reports.
Rejection of the treaty would represent a humiliating defeat for the administration, which has led an international campaign for the treaty.
It has been signed by 154 countries, but 21 of the 44 nuclear-capable nations, including the U.S., Russia and China, have not yet ratified it.
In the absence of a deal, both sides were preparing to begin the debate Friday.