BOSTON — A proposed $250 million cut to the Pentagon’s $549 million budget request for the Airborne Laser next year would delay a crucial demonstration of the futuristic system by about three years, according to a U.S. Missile Defense Agency (MDA) official.

That demonstration, in which the modified Boeing 747 aircraft equipped with a high-powered laser will attempt to shoot down a target missile, currently is scheduled for 2009. But the MDA and its Boeing-led Airborne Laser contracting team will not meet that schedule if the recommendation by the House Armed Service Committee, which finalized its version of the 2008 defense authorization bill May 9, becomes law.

The proposal supersedes a more drastic cut of $400 million that was proposed May 2 by the House Armed Services strategic forces subcommittee, but its implications are still significant, said Greg Hyslop, vice president and Airborne Laser program director at Boeing Missile Defense Systems of Arlington, Va.

“The committee’s bill still reduces the president’s budget request for this vital capability by almost half,” Hyslop said May 10 in a written response to questions. “A reduction of that magnitude would have a significant impact on the program. We will continue to work with Congress and MDA to achieve full funding” for the program in 2008, he said.

Congressional aides said, however, that the Airborne Laser likely faces a similar reduction when the Senate Armed Services Committee begins marking up its version of the 2008 defense authorization bill May 22.

The Airborne Laser is the MDA’s primary boost-phase missile defense system, and the upcoming shoot-down test is considered key to the program’s future. The test has been delayed several times since Boeing won the prime contract in 1996 .

Most recently, the test was pushed from late 2008 to August 2009, a delay that Hyslop, in a conference call with reporters May 8, said would increase the value of Boeing’s contract from $3.6 billion to $3.8 billion. The original Airborne Laser contract value was about $1 billion.

Hyslop and representatives from Airborne Laser subcontractors Lockheed Martin and Northrop Grumman said during the conference call that the program is making progress and surmounting its technical challenges. Hyslop said the team is on the verge of demonstrating a revolutionary capability that could be used for air and cruise-missile defense as well as ballistic-missile defense.

The initial Airborne Laser aircraft is a prototype intended for demonstration purposes. The MDA hopes to build a second, more-capable version that also would be a demonstration platform but which could be pressed into action in an emergency, the MDA official said.

Hyslop said the Boeing team is preparing a cost estimate for the second Airborne Laser as a follow up to a similar estimate from the Pentagon. He de clined to divulge the Pentagon’s estimate, as did the MDA official, who said the results, which were shared with Congress last spring, were “for official use only.”

The current study will take into account progress made on the program over the past year and is expected to wrap up this summer, the MDA official said.

If approved, the second Airborne Laser platform likely would be built by the Boeing-led team because of the “extremely unique design and complexity of the first ,” the MDA official said.

Victoria Samson, a missile defense analyst with the Center for Defense Information, a Washington-based think tank, said the price tag for a second Airborne Laser likely will be measured in the billions of dollars, even taking into account the lessons learned and technical risks retired in building the first. Because of the system’s immense complexity, it does not really lend itself to production-line efficiencies that can bring down the cost of other large military platforms, she said.

The Airborne Laser was not the only missile defense program on which the full House Armed Services Committee adjusted the recommendations of the strategic forces subcommittee. For example, the full committee trimmed the MDA’s $227 request for the Kinetic Energy Interceptor — a high-speed rocket designed to engage missiles in all phases of flight — by $50 million. The reduction still allows for a flight test of the booster in 2008, according to Rep. Ellen Tauscher (D-Calif.), chairwoman of the strategic forces subcommittee, who proposed the cut as part of a larger amendment.

The full committee upheld the subcommittee’s recommendation to trim $160 million from the MDA’s $310 million request for work on missile defense sites in the Czech Republic and Poland. However, the committee invited the Pentagon to request that the funding be reinstated via a reprogramming should those countries formally agree by next year to host the sites.