WASHINGTON -- Congress' failure to pass a 2011 defense budget bill is jeopardizing the military's effort to send more surveillance and attack drones into Afghanistan, as well as stymieing plans to buy a new Navy submarine, Army combat helicopters and other major weapons systems, defense leaders say.

As Pentagon officials fan out across Capitol Hill, pleading for lawmakers to approve the 2011 spending levels proposed by the Obama administration, they also are hitting lawmakers where it hurts -- in their congressional districts and states. Less money in the budget, the officials said, will put at risk thousands of jobs and construction projects nationwide.

Right now the U.S. is operating under a stopgap budget extension that funds the federal government at the 2010 level. And Republicans, who control the House and gained ground in the Senate in the 2010 elections, have said they intend to use this opportunity to end dozens of programs and slash spending on many more.

Overall, the Army, Navy and Air Force say they would lose at least $26 billion if the spending level stays largely the same as 2010, compared with the larger 2011 budget request made by the administration.

"This is going to have a really significant impact on us in four main areas," Navy Secretary Ray Mabus said. "And time is not on our side. By March we'll be almost halfway through the fiscal year. Even if you get (the budget) done in March, it still is going to be hard to do some of these things."

Laying out a plan for $35 billion in program cuts and terminations Wednesday, Republicans said they were determined to keep their pledge to the American people to rein in federal spending.

Some, including Rep. Jeff Flake of Arizona, said he'd prefer to see even more savings.

But other lawmakers have spoken out against cutbacks in defense spending.

Sen. Susan Collins, R-Maine, said in a letter to Senate Majority Leader Harry Reid that is unacceptable that the military, in its 10th year of war, be expected to absorb such budget reductions.

Military officials were quick to say they will make sure that forces in Iraq and Afghanistan get what they need. But the cuts will affect training and equipment for troops at home -- and many of those are slated for future deployments to the war zone.

On Wednesday, Republican lawmakers rolled out a plan to give the Pentagon about $518 billion, which is about $1 billion more than the 2010 level, but still well short of the $531 billion recommended in Obama's 2011 request. There were no details on how much each military service would get.

If the totals in the stopgap spending bill stick, the Army would lose as much as $13 billion, the Air Force about $7 billion and the Navy nearly $6 billion.

Living with those cuts, military leaders said, would force costly delays in major programs, such as the purchase of 24 hunter-killer Reaper drones used heavily in Afghanistan, the construction of a new Virginia-class submarine, a naval destroyer and an E-2D Hawkeye airborne command and control aircraft.

As an example, the decreased funding would give the Air Force $1.2 billion less for salaries and personnel costs than the 2011 funding bill, and would require shifting money around later this summer in order to meet the payroll in the final quarter of the fiscal year.

"The trade-offs are real," said Jamie Morin, assistant Air Force secretary for financial management. "We would have to pull that money from other major programs."

Air Force Maj. Gen Alfred Flowers, the deputy assistant secretary for the budget, said 36 construction projects already have been deferred, and that number could go as high as 129, for a total of $1.1 billion, if the money is not restored.

The Navy said the cuts have delayed and could jeopardize nearly 90 construction projects in 13 states, threatening up to 7,300 jobs. And it could force cancellation of major maintenance on ships, aircraft and engines that would affect another 1,300 private sector jobs.

At the same time, program delays could trigger price increases down the road. Canceling the order for a submarine this year would increase the cost of one that is already being built, Mabus said. He added that the cuts would cost the Marine Corps about a third of its procurement budget for equipment.

Army officials said the cuts could delay the awarding of contracts for a new ground combat vehicle, putting delivery of the first vehicle behind schedule. And there would be no money to buy four new Chinook transport helicopters that are used extensively in Iraq and Afghanistan.

As for local impact, the Army said there would be no money to refurbish Humvee utility vehicles, and officials could be forced to shut down production lines at the Red River Army depot in Texas and the Letterkenny Army depot in Pennsylvania.