A key US lawmaker leading the fight against military spending cuts has warned that dramatic new reductions could force the United States to shift from an all-volunteer military and reinstate the draft.

House Armed Services Committee Buck McKeon, a Republican, told Fox News television on Monday that lawmakers "need to understand what it's going to mean to keep an all-volunteer force."

"Do we want to reinstitute the draft? Some of the cuts we're talking about would take over 200,000 out of end strength from our military," McKeon said in remarks also reported in the Washington Post on Tuesday.

The lawmaker said that an August debt-limit deal included $465 billion of defense spending cuts over ten years, and warned that "it'll be over another $500 billion" in automatic cuts to military programs if a new "supercommittee" fails to find $1.2 trillion in deficit cuts over ten years in a few weeks.

"We understand that defense has to be on the table, just as everything else is," he said, but draconian cuts to the Pentagon would raise the question of "who's going to have our back the next time we're attacked."

If the "supercommittee" fails to agree on a plan by November 23, and Congress fails to pass it by December 23, that would trigger $1.2 trillion in automatic cuts to military spending and a popular health care program come January 2013.

The cuts were designed to be so unpopular with Republicans and Democrats that they would force the 12-member panel to find a compromise, and force the overall congress to back the compromise.

But senior Republicans have been working to fight against new cuts to defense spending as part of the committee's work, warning such reductions could endanger US national security in the face of a rising China and could deepen the US economic downturn by swelling the ranks of unemployed.