Updated June 19 at 2:30 p.m.

WASHINGTON – A senior U.S. Missile Defense Agency official expressed concern June 18 about a House spending bill that provides some 22 percent less funding than requested for a new kill vehicle and said the impact could spill over onto other programs.

The MDA requested $278 million next year for the Redesigned Kill Vehicle, or RKV, under a budget line dubbed Improved Homeland Defense Interceptor. The effort, identified by the MDA’s director as a top priority, addresses reliability concerns with the Exoatmospheric Kill Vehicles that top the interceptors now deployed to protect the U.S. homeland against missile attacks.

But the House of Representatives, whose Republican leadership is generally supportive of missile defense, recently passed a bill that provides just $217 million for the RKV. That bill must be reconciled with a Senate bill that recommends providing $298 million next year.

“We are concerned, I’ll be candid with you,” U.S. Air Force Brig. Gen. Kenneth Todorov, the MDA’s deputy director, said at a breakfast here June 18. “We’ve seen the marks from some of the committees on the Hill. We’re watching them carefully. Some of them concern us and we sure hope we get some of this worked out in conference because the RKV is really at the forefront” of efforts to improve the U.S. territorial shield, he said.  “We need to get that settled and get our plan underway,” he added.

The MDA hatched the RKV program last year following a string of intercept failures of the Boeing-built Ground-based Midcourse Defense system, two of which were attributed to the Exoatmospheric Kill Vehicle. The Raytheon-built kill vehicle, designed to destroy incoming missile warheads by direct impact, was rushed through development and has not had a significant design change in more than a decade.

The RKV is now the cornerstone of MDA’s most recent batch of research and development projects. Last November, Navy Adm. Jonathan Greenert, the chief of naval operations, and Gen. Raymond Odierno, the chief of staff of the Army, said in a letter to Chuck Hagel, then the secretary of defense, that the MDA’s “acquisition-based strategy is unsustainable in the current fiscal environment.” Todorov agreed that the agency’s budget focused too little on research and development and called the current long-term trend “unsustainable.”

In trimming the request for the RKV, a move that also has drawn opposition from the White House, the House Appropriations Committee cited a “lack of justification materials and schedule” information on the program.

Todorov said MDA leaders have been meeting with lawmakers to explain the agency’s plan.

“I absolutely do not think the mark is a disagreement with where we’re going with the program,” he said. “We’ve had really widespread support for it. There could be a lack of understanding of our strategy of how we’re going to do it.”

The MDA intends to lead the RKV development effort by drawing on the best ideas from three previously submitted industry concepts and then hold a competition for the production work. Production is tentatively slated to begin in 2018.

If the House mark stands, Todorov said, it could undermine the effectiveness of another top MDA priority, the Long Range Discrimination Radar.

The radar, which would be able to better distinguish between actual warheads and decoys or debris, is expected to be operational in 2020. The MDA expects to award a full-scale development contract before the end of 2015.

“If we don’t take the kill vehicle to the next level, the investment we’re making in other areas isn’t maximized,” Todorov said. “We’re hopeful we’ll get some relief.”

Todorov also said the MDA still needs a layer of space-based sensors for target tracking and discrimination. Previous MDA efforts to field missile tracking satellite constellations have floundered due to their high cost.

“We’ve got to find a way to do it,” Todorov said. “From a missile defense standpoint, we can’t just ignore the possibility of going [to space] because of the cost.”

The MDA is in the midst of an analysis of alternatives for its future network of land-, sea- and space-based sensors. That analysis is expected to be completed later this year.

Todorov said the agency needs to find creative ways to field space-based sensors and that one possibility may be “payloads on other payloads.” The MDA already has plans for a network of experimental kill assessment sensors hosted aboard commercial satellites that would start launching in late 2016.

Mike Gruss covers military space issues, including the U.S. Air Force and Missile Defense Agency, for SpaceNews. He is a graduate of Miami University in Oxford, Ohio.