In a new report, a secretive federal panel has concluded that programs to extend the life of the nation's aging nuclear arms are sufficient to guarantee their destructiveness for decades to come, obviating a need for a costly new generation of more reliable warheads.

The finding, by the Jason panel, an independent group of scientists that advises the federal government on issues of science and technology, bears on the growing debate over whether the United States should ratify the Comprehensive Test Ban Treaty or, instead, prepare for the design of new nuclear arms.

Sen. Jon Kyl of Arizona and other Republicans have argued that concerns are growing over the reliability of the United States' aging nuclear stockpile and that the possible need for new designs means that the nation should retain the right to conduct underground tests of new nuclear weapons.

The testing issue is expected to flare in the months ahead when the Obama administration submits the test ban treaty for ratification by the Senate, where it faces a tough fight. The White House is building a case that advanced technologies make any additions to the nuclear arsenal unnecessary and also allow the United States to verify that other countries are refraining from underground testing.

Backers of the test ban hailed the new report as supporting President Barack Obama's position. “;It kills the hysteria and builds the case for what the president and the Democrats want to do,”; said Daryl G. Kimball, executive director of the Washington-based Arms Control Association.

Jeffrey G. Lewis, a nuclear specialist at the New America Foundation, a Washington research group, said in a blog posting that the report “;should drive a stake through the heart”; of the Reliable Replacement Warhead, a Bush administration initiative to build a new generation of nuclear arms.

The Jason report, mandated by Congress, centers on an Energy Department program that refurbishes the nation's aging nuclear arms. As central players in the Cold War, the warheads were designed for relatively short lifetimes and frequent replacement with better models. But such modernization ended after the United States quit testing nuclear arms in 1992, and all weapons that remain in the arsenal must undergo the refurbishment process, known as life extension.

The Jason panel said that it had found no evidence that the accumulated changes from aging and refurbishment posed any threat to weapon destructiveness, and that the “;lifetimes of today's nuclear warheads could be extended for decades, with no anticipated loss of confidence.”;

The report warned, however, that federal indifference could undermine the refurbishment program. “;The study team,”; the report said, “;is concerned that this expertise is threatened by lack of program stability, perceived lack of mission importance and degradation of the work environment.”;

Jason panels are organized by Mitre Corp., a nonprofit organization in McLean, Va., that does work for the Defense Department. Typical sponsors include the military, the intelligence community and the Department of Energy. Most Jason reports are classified secret, and only the executive summary of this one, “;Lifetime Extension Program,”; was made public Thursday.