The Army’s most ambitious and expensive program is facing an uncertain future as military leaders struggle to repair war-torn equipment and grow the service’s force.

Defense Secretary Robert Gates told the Senate Armed Services Committee Wednesday that the Future Combat Systems (FCS) could be at the mercy of new budgetary constraints brought on by the wars in Iraq and Afghanistan, along with other military priorities.

“Frankly, it is hard for me to see how that program can be completed in its entirety,” Gates said. “In light of what are inevitably going to be pressures on the defense budget in the future, I think that that one is one that we will have to look at carefully.”

Army leaders have long envisioned a major transition in the way their forces operate, pushing for the lighter and more agile combat brigades in years to come.

At the same time, the Army will need approximately $260 billion by fiscal year 2011 to grow its force, repair equipment damaged in the Iraq and Afghanistan wars and buy new technologies, such as the ones that are part of FCS.

“It looks as if there’s about $141 billion roughly committed. There’s a big delta,” said Sen. Jack Reed (D-R.I.), who asked Gates whether he was concerned about balancing modernization initiatives and growing the force.

Proponents say the FCS would make the Army a more agile and easily deployable force with self-sufficient units.  The price tag of the program has been estimated between $160 billion and $200 billion. So far the program — contracted out to Boeing and SAIC — has been restructured several times.

Congress has been cutting funds from the program and expressing criticism of the progress of the technology development. For this fiscal year, lawmakers trimmed the program by $200 million in addition to about $825 million in cuts during the previous three years. The Army has complained that those cuts have caused several program revisions and have in part delayed the program.

FCS could likely face more cuts in the fiscal 2009 bills. The Army requested $3.6 billion for the program in fiscal 2009.

“One of the things that I think is attractive about the way the Army has approached [FCS] is that, as they are developing new technologies, they are putting them into the field right away, instead of waiting to bring this thing full-up,” Gates said.

Pentagon officials and congressional sources have said that the Army is also facing a dilemma in coming years over the purpose and make-up of the FCS — lighter vehicles protected by high-tech situational awareness such as knowing the location of roadside bombs in advance or using radars to detect and track incoming rockets.