U.S. Defense Secretary Robert Gates is calling on Congress to support strategic cuts to the defense budget, while ensuring the military remains strong enough to respond to the threats facing the nation.

Testifying before a Senate appropriations subcommittee Wednesday, Gates said the overarching goal is to preserve a U.S. military capable of meeting crucial national security priorities even if fiscal pressure requires a smaller force.

Both he and the top U.S. military officer, Admiral Michael Mullen, warned against making budget cuts in a way that would hollow out the force, leaving it with a lack of proper training, equipment and personnel.

President Barack Obama has called for an additional $400 billion in cuts to security spending to help rein in the nation's massive deficit.

Wednesday's hearing marks Gates' last appearance on Capitol Hill before he retires. He told the committee that leading the military during the past four-and-a-half years has been “the greatest privilege” of his life.

Testifying alongside Gates, Mullen said funding also is needed to help soldiers and their families cope with the strain of nearly a decade at war, highlighting proposed investments in health care and housing.

Mullen also warned against changing U.S. military assistance to countries like Egypt and Pakistan, saying any changes should be considered only with an “abundance of caution” and appreciation for the long view, rather than in the flush of public passion and urgency to save money.

The nominee to replace Gates as defense secretary, Leon Panetta, has acknowledged the need to make “tough decisions” to trim the defense budget.

Panetta, who currently heads the Central Intelligence Agency, testified at a Senate hearing on his nomination last week that the challenge will be to eliminate wasteful spending while protecting the core elements needed for the nation's defense.