A key congressional subcommittee slashed President Bush's NASA budget request by more than $1 billion yesterday, dealing a sharp early blow to the administration's efforts to set in motion an ambitious plan to send humans to the moon and Mars.

The panel eliminated $438 million the administration had requested to begin work on a new "crew exploration vehicle" to replace the space shuttle, cut its request for medical and biological research in space by $103 million, and eliminated $70 million for lunar exploration.

"The bulk of these savings come from the elimination of funding for new initiatives," said a statement from the House Appropriations subcommittee that oversees the departments of Veterans Affairs and Housing and Urban Development and other scientific and unrelated agencies.

The subcommittee passed by voice vote its proposed $90.8 billion 2005 spending bill for those programs. The measure is still awaiting action by the full House Appropriations Committee and the House. It then goes to the Senate.

NASA's share was $15.1 billion, down $229 million from this fiscal year and $1.1 billion below the president's request, effectively slowing the administration's plans to reorient NASA's priorities toward a return to the moon and eventual human space travel to Mars.

The committee made it clear in its as-yet-unpublished report on the proposed legislation that it did not fully agree with the president's priorities: "While the committee is supportive of the exploration aspect of NASA's vision, the committee does not believe it warrants top billing over science and aeronautics," said the report, a copy of which was obtained by The Washington Post.

Still, lawmakers from both parties were reluctant to describe the cuts as a rebuke to Bush's "Vision for Space Exploration." Instead, lawmakers noted strictures for every agency in the subcommittee's portfolio:

"This fiscal policy is going to squeeze . . ., [and] scientific, research and social programs are not going to be carried out," the subcommittee's ranking Democrat, Alan B. Mollohan (W.Va.), said in a telephone interview. "NASA is not immune to that. It's a very difficult bill, and no constituency is going to be satisfied with it."

NASA also took a positive tone. Glenn Mahone, a spokesman for NASA Administrator Sean O'Keefe, noted that "even within these very tight constraints, the subcommittee fully funded the shuttle and Mars exploration programs and expressed support for the new vision."

But while the Mars program got $691 million after a spectacular year punctuated by the success of the rovers Spirit and Opportunity, congressional sources said the $4.3 billion allocated for the shuttle may fall short by $450 million to $760 million as NASA pays the bills for the shuttle's return to flight after last year's Columbia disaster.

The committee also expressed skepticism that the administration can finish building the international space station by 2010 and then retire the shuttle. Knowledgeable congressional staffers, who declined to be identified by name because of committee policy, suggested that this view contributed to lawmakers' decision not to fund the crew exploration vehicle.

"NASA needs to reevaluate this date in the context of the current budget environment and the technical challenges associated both with return-to-flight activities and the new system development needs," the panel's report said.

The report also urged NASA not to forgo the option of a shuttle servicing mission to the Hubble Space Telescope. O'Keefe has all but ruled out a shuttle mission to Hubble and is focusing instead on servicing of the telescope with a robotic spacecraft.

The subcommittee report earmarked funds for both aeronautics research, an area NASA had sought to cut, and materials research in space, an endeavor the agency is seeking to eliminate to focus on the medical and biological research it needs to serve the moon-Mars initiative. Congressional sources attributed the panel's decision to cut $12.4 million from a mission to explore the moons of Jupiter as a casualty of budget austerity.

This was felt by other agencies in the bill. Even though the panel boosted spending on the Department of Veterans Affairs by $4.3 billion over 2004, Mollohan said the department needed $1.3 billion more for VA housing. Also short, he said, was federal assistance for low-income renters of apartments and houses, despite a proposed funding level of $14.7 billion, $491 million more than in 2004.

The bill proposed paring the budget of the National Science Foundation to $5.5 billion, $111 million below 2004 and $278 million below the president's request. The Environmental Protection Agency's spending was set at $7.8 billion, $613 million below its 2004 level.