Lawmakers overseeing defense spending are moving to block or modify deep cuts proposed by Defense Secretary Robert M. Gates, setting up a key vote this week that could help determine the success of the administration’s attempt to shrink the Pentagon’s budget.

Excluding the wars in Afghanistan and Iraq, the administration has proposed a $553 billion budget for the Pentagon next year — less than a 1 percent increase over what it requested for 2011 — and the House Armed Services Committee is expected to vote this week on the fiscal 2012 defense authorization bill.

But the panel’s subcommittees last week voted to prohibit a proposed increase in fees paid by retired service personnel for Tricare, the military’s health program; set the stage for possible recompetition of the controversial engine for the Air Force F-35 Joint Strike Fighter; and required studies before the Marine Corps can go ahead with a new proposed amphibious landing craft to replace the multibillion-dollar Expeditionary Fighting Vehicle (EFV).

The subcommittees have also added funds to programs that the Pentagon did not seek. For example, $425 million has been added to the proposed budget to keep production lines open for the Bradley Fighting Vehicle and the Abrams M1 tank. The Pentagon had proposed shutting down those lines for three years to save money.

Committee Chairman Howard P. “Buck” McKeon (R-Calif.), speaking before the Heritage Foundation last week, said: “Folks, the defense industry cannot be turned on and off like a light switch. Shutting down production then restarting at a later date costs more than just keeping the lines open.”

Not all the changes approved by the subcommittees will go unchallenged.

For example, on the annual Tricare enrollment fees, McKeon plans to offer a compromise this week, outlining a proposal that would involve some increase in premiums but not as much as the increase Gates had sought. The defense secretary had proposed an increase of $2.50 a month for military retirees still working and under 65, and $5 a month for those with families. That would raise premiums to $520 a year for family coverage, and half that, $260 a year for singles.

The personnel subcommittee members took no action to change another Gates proposal — one to increase the costs for retirees purchasing prescription drugs from local pharmacies, apparently to stay within their own budget limitations. That issue may come up when the full committee acts on the bill this week or when it reaches the House floor, since local druggists are popular with the legislators.

The Gates decision to stop funding General Electric’s alternative engine for the F-35, which would save as much as $3 billion, has been challenged by new language in a subcommittee-approved bill. Because members believe the remaining Pratt & Whitney engine will need more thrust because of increased weight of the fighter, the bill prohibits the Pentagon from paying for such an improvement “unless the Secretary of Defense ensures that funds are made available and expended in fiscal year 2012 for two options for the F-35 propulsion system.”

McKeon praised General Electric for continuing to fund the engine through 2012 on its own after the Pentagon stopped government payments last month. “I will accept and support their approach,” McKeon said. “They believe in their engine, and they believe in competition.”

To reinforce the committee’s basic message of engine competition, language was placed in the bill that would require the secretary of the Air Force, in developing the next generation long-range strike bomber, “to develop a competitive acquisition strategy for the propulsion system.”

Rep. Todd Akin (R-Mo.), chairman of the subcommittee on readiness, made clear in a recent hearing that he believed “canceling the EFV was a bad decision, but throwing more money at the new program without doing their homework first is a recipe for more wasted money.” His report on the bill notes that it could cost as much as $9 billion to upgrade or replace the current amphibious assault vehicle now that the EFV has been canceled.

Akin’s bill in effect prevents spending further funds for reasons other than the performance of minor upgrades to the current amphibious landing vehicle. In the meantime, under the bill, a new acquisition strategy would have to be developed and sent to the committee before a new amphibious combat vehicle program is started.