The anticipated drawdown of U.S. forces in Iraq and the ongoing economic crisis are likely to force the 111th Congress and the next president to weigh difficult cuts in Defense Department spending.

The Defense budget is “going to come down, there is no question about it,” House Appropriations Subcommittee on Defense Chairman John Murtha (D-Pa.) told CongressNow during a recent interview.

Sen. Jack Reed (D-R.I.), a member of both the Senate Armed Services and Appropriations committees, also said there would be “huge pressure” to trim the Pentagon budget in coming years as war spending declines. The “wild card” in determining whether there would be deep cuts in Defense, he said, would be the severity and federal cost of the ongoing crisis in financial markets.

Since the Iraq War began, the Bush administration has relied on hefty emergency spending bills, also dubbed supplementals, to provide hundreds of billions of dollars in war spending not proposed in annual budgets.

For example, in 2008 the Pentagon received $479.6 billion in annual appropriations and additionally approved as emergency spending most of the $196 billion sought by the White House for operations in Iraq and Afghanistan.

Lawmakers, however, have become increasingly critical of the emergency bills, saying at this point in the conflict the administration should be able to predict the cost of the wars and seek that spending in its annual budget. To date, emergency spending costs for the war have topped $500 billion.

Acting Air Force Secretary Michael Donley said at the Air & Space Conference and Technology Exposition in Washington, D.C., earlier this month that he has told his staff to begin planning for the end of supplemental spending bills.

“I come at this as an old comptroller,” Donley told reporters. “How quickly national priorities can shift.”

Donley said the Air Force’s primary source of funding for buying and operating intelligence, surveillance and reconnaissance systems used for the wars has come from supplemental bills. To ensure that the service is not caught off guard and forced to make budget cuts, Donley said his staff is looking at “which elements need to be transferred back to baseline budget,” and then finding “homes” for those projects.

Murtha warned that more difficult decisions could be on the horizon for the services as the U.S. public begins to demand that money is spent on domestic projects instead of the Iraq War. “The public wants money spent on U.S. infrastructure,” he said.

Murtha predicted the Pentagon would be forced to choose between making cuts to personnel, facilities or weapons spending. With the Army and Marine Corps due to expand over the next several years, most Defense budget experts believe the Pentagon may have to target weapons spending to cover personnel expenses.

At the Air & Space Conference, Air Force Chief of Staff Gen. Norton Schwartz said prioritizing procurement items would be a challenge for the Air Force. The service has several key weapons projects pending, such as building a new fleet of aerial refueling tankers as well as bomber aircraft and fighter jet fleets.

“It’s multiple things at the same time,” Schwartz said.

Not only will the service officials have to tighten their own belt, but they will have to be prepared to defend their own needs against other services, Donley warned.

“We must prepare … to defend our resources under constrained budgets,” Donley said. He added that tight purse strings would likely force the services to team up to build weapons they can both use — a move that would save developmental dollars.

George Cahlink contributed to this report.