The top lawmakers on the Senate's defense panel on Friday recommended that a special committee searching for ways to slash the deficit consider some of President Barack Obama's proposed changes to health and retirement benefits for the military.

In separate letters to the bipartisan panel, Sen. Carl Levin, D-Mich., chairman of the Armed Services Committee, and Sen. John McCain, R-Ariz., signaled they were open to cost-saving steps in military benefits, recommendations that have already attracted fierce opposition from powerful groups of retired officers and veterans resistant to change.

The Pentagon's health care costs have skyrocketed from $19 billion in 2001 to $53 billion, but lawmakers and various groups argue that members of the military and their families sacrifice far more than the average American, with a career that includes long and dangerous deployments overseas that overshadow civilian work. Health and retirement benefits help attract service members to the all-volunteer force.

Levin and McCain said they would support establishing an annual enrollment fee for TRICARE for Life, the health care program that has no fee for participation. Obama had proposed an initial annual fee of $200.

"This proposal would be the first such change since Congress established this program in 2001, a period during which national health care costs have risen significantly," McCain wrote.

Levin said future increases in fees should be tied to the same index used to determine hikes in the TRICARE Prime program, which has the lowest out-of-pocked expenses.

"Whichever benchmark is ultimately agreed upon, annual fee increases for retirees over the age of 65 should be the same as annual fees for working age-retirees," Levin wrote.

McCain also urged the so-called supercommittee to consider restricting working-age military retirees and their dependents from enrolling in TRICARE Prime, which has the lowest out-of-pocket expenses. The retirees could still enroll in other TRICARE programs. McCain pointed out that the Congressional Budget Office has estimated that such a move would save $111 billion over 10 years.

Active-duty personnel still would be enrolled in the program automatically.

McCain, who was Obama's rival for the presidency in 2008, also said he supported Obama's proposal for a commission to review military retirement benefits that should consider changes to the military compensation system. He said he agreed with Defense Secretary Leon Panetta, who said those currently serving in the military should be "grandfathered" in, so expected benefits aren't reduced.

Levin also backed creation of a commission, but suggested that it look at all elements of military compensation, including basic pay, allowances such as housing, incentive pay and the tax structure for military pay. He said current service members should be grandfathered in "to avoid breaking faith with the force."

Veterans groups challenged Obama's proposals last month and quickly mobilized to fight any effort by the supercommittee to adopt the recommendations.

"Some in Washington want to make those who sacrifice and serve the most, sacrifice more," Joe Davis, a spokesman for the Veterans for the 2 million-member Veterans of Foreign Wars, said Friday. "It infuriates us when they talk about military benefit programs as entitlements. They're something you absolutely paid for up front through your service and sacrifice to the country."

Davis said VFW members are being urged to contact their congressmen and senators.

Levin and McCain also told the supercommittee they reject any deeper cuts in overall defense spending beyond the 10-year, $450 billion cuts already set by the administration and Congress.

"I fully support the president's decision not to propose any additional reductions in defense spending limits beyond those he has already called for," he said.