The Bush administration yesterday sent its lobbying forces to Capitol Hill to save the president's defense budget from further erosion after the House Armed Services Committee voted Tuesday night to kill the B-2 "stealth" bomber, block mobile missile plans and slash funding for strategic defense and a host of new weapons.

Defense Secretary Richard B. Cheney met with Senate Democrats to seek their support in the Senate battle over the Air Force bomber whose technology, mission and $865 million pricetag have become a symbol of the struggle to redefine post-Cold War national priorities. Senate debate on the B-2 and the $289 billion version of the defense bill approved by the Senate Armed Services Committee begins today.

Sen. Sam Nunn (D-Ga.), chairman of the panel, has warned the administration that it will have to fight to save the B-2, whose carbon-fiber skin and batwing shape make it extremely difficult to detect on radar.

President Bush was scheduled to make a major speech on defense today in Aspen, Colo.

"Right now, we're on the losing side of the B-2 issue," said one Senate staff member. "There are a lot of defections on the Republican side . . . and things have only gotten worse" following the bipartisan 40 to 12 vote in the House committee to report out a $283 billion defense bill without further funding for the bomber, built by the Northrop Corp. One B-2 has been flight-tested and 15 are under construction.

Other administration officials, including Ronald Lehman, director of the Arms Control and Disarmament Agency, were said by Senate sources to be calling members to marshal support for the budget request to modernize strategic forces.

Through the week, senators from both parties have been called to the White House for what a Senate aide described as "arm-twisting sessions" on defense. Cheney met with the Senate GOP caucus Tuesday and the administration is working closely with Nunn, ranking minority Armed Services Committee member John W. Warner (R-Va.), J. James Exon (D-Neb.) and Strom Thurmond (R-S.C.) to coordinate strategy for Senate debate on the defense spending plan and the B-2's fate.

Meanwhile, at a morning meeting with reporters, Rep. Les Aspin (D-Wis.), chairman of the House panel, defended the vote to kill the B-2. "You've got to take something out, and the one candidate with the lowest priority of the five major weapons systems was the B-2," he said.

Aspin said he also favored killing the Air Force's Advanced Tactical Fighter and the Army's light helicopter, while continuing research and development in the programs. The committee cut funding for full-scale development of both systems, whose total pricetag exceeded $100 billion.

At the same time, Aspin said he now sees the virtue of building the C-17 transport and the V-22 Osprey tilt-rotor aircraft. The latter has been the subject of intense lobbying by the Texas and Pennsylvania delegations.

Referring to the collapse of the Soviet-led Warsaw Pact in Europe, Aspin said, "None of the things that have happened have improved the case for the B-2. Some of the things that have happened have improved the case for the V-22."

Aspin also sought to emphasize that the decision to cancel research funds for two mobile intercontinental missiles was not the death knell for the land-based missile force.

Quoting from the report of the closed-door committee session, Aspin said the vote to cut research and development funds for the MX-Rail Garrison and the Midgetman was not an attempt to kill both, but an attempt to put Bush on notice that "the two-missile ICBM modernization program has failed to achieve the political consensus necessary for deployment of both systems."

The White House now can submit a new missile modernization plan and spend up to $610 million allocated for research in 1991, but Congress can reject the new plan during a 90-day review period after it is submitted, Aspin said.

Rep. John M. Spratt Jr. (D-S.C.), who chairs the nuclear facilities panel, said the House bill terminates the Pentagon's plan to build the SRAM-T short-range nuclear missile that would be launched from aircraft stationed at NATO bases in Europe.

The panel also voted to kill a Navy nuclear depth charge program and establish a $150 million fund to address safety concerns disclosed earlier this year by The Washington Post relating to the risk of accidental detonation of the conventional explosives in some nuclear weapons.