Fresh off a slate of planned military benefits changes and trims, congressional defense leaders on Tuesday said they are already looking ahead to more entitlement and personnel reforms in 2016.

Sen. John McCain, R-Ariz., the Senate Armed Services Committee chairman, called growing military personnel costs "one of our greatest challenges" in coming years, saying that "we're going to have to make some tough decisions" soon.

His comments came at a Brookings Institution event about the fiscal 2016 defense authorization bill, which was approved by Congress earlier this month but faces a looming presidential veto.

The measure would allow a lower-than-anticipated pay raise for troops starting in January and includes trims in the growth of military housing stipends, new co-pays for some military drug prescriptions and plans to scale down the commissary benefit.

Pentagon officials have said the changes are needed to help rein in personnel costs, but outside advocates lament that the compensation moves will dilute military families' purchasing power.

The defense bill also includes an overhaul of the traditional, 20-year military retirement system, based on recommendations from a Military Compensation and Retirement Modernization Commission report released earlier this year.

That panel also pushed for an overhaul to military health care offerings. Rep. Mac Thornberry, R-Texas, chairman of the House Armed Services Committee, said work on that issue will begin in the coming weeks.

House Armed Services Committee Chairman Rep. Mac Thornberry, R-Texas., speaks on Capitol Hill in Washington, Wednesday, June 17, 2015, during a hearing with Defense Secretary Ash Carter and Joint Chiefs of Staff Chairman Gen. Martin Dempsey on the U.S. policy and strategy in the Middle East. (AP Photo/Susan Walsh)
House Armed Services Committee Chairman Rep. Mac Thornberry, R-Texas., speaks on Capitol Hill in Washington, Wednesday, June 17, 2015, during a hearing with Defense Secretary Ash Carter and Joint Chiefs of Staff Chairman Gen. Martin Dempsey on the U.S. policy and strategy in the Middle East. (AP Photo/Susan Walsh)

Rep. Mac Thornberry, R-Texas, chairman of the House Armed Services Committee, said lawmakers soon will take up the issue of military health care reform.

Photo Credit: Susan Walsh/AP

"Tricare reform is going to be a key focus because access to care is not what it should be," Thornberry told reporters after the event. "There are a number of areas where we ask: 'Are we best positioned to recruit and retain top quality people in today's work environment?' "

The commission has recommended a complete overhaul of the military health system, to include dumping Tricare, realigning medical commands and better integrating Defense Department care with Veterans Affairs medical offerings.

Lawmakers thus far have been wary of changes on that large a scale, but Thornberry has promised a close examination of the ideas.

Before work on future reforms and authorization bills can begin, lawmakers still need to see what happens with the pending legislation. The bill is expected to be sent to the White House late Tuesday afternoon, and President Obama will have 10 days to veto the measure.

Thornberry and McCain have argued that scuttling the military policy bill would have devastating effects on national defense, but Obama has said that signing the bill and agreeing to Republican budget plans would endanger a range of domestic, nondefense programs.