Defense Secretary Leon Panetta is warning Congress that possible sweeping cuts to the defense budget would put millions more out of work and add a percentage point to the country's unemployment rate, a spokesman said.
The Pentagon described a dire scenario if a congressional "supercommittee" fails to agree by November 23 to trim $1.2 trillion from government deficits, which would trigger deep automatic cuts across the federal government.
"We believe that would result in job cuts that would add one percent to the unemployment rate," said press secretary George Little, citing Defense Department estimates.
"So we're not talking about just military jobs. We're also talking about jobs in the private sector that support the innovation and creativity and capabilities that we need to keep America strong," he told reporters.
In phone calls and meetings with members of Congress, Panetta has shared the Pentagon's gloomy estimates, according to Little.
Panetta wanted "to make it very clear" that automatic cuts represented "a red line that this government should not cross," Little said.
With high unemployment a politically-charged issue, the alarming forecast was the Pentagon's latest salvo as it seeks to fend off mandatory reductions that could be triggered if Congress fails to agree long-term spending cuts.
Panetta has argued that any defense cuts beyond already planned reductions of about $350-400 billion over the next decade would have "devastating" consequences for the world's most powerful military.
If the congressional panel fails to agree on how to slice the budget before the end of the year, it would trigger automatic defense cuts "in the neighborhood" of one trillion dollars, Little said.
The cutbacks would jeopardize military jobs and roughly 3.8 million jobs in the country's giant defense industry, he said.
But the Pentagon spokesman did not offer a breakdown on precisely how many jobs would be lost in the government and military under the sweeping reductions.
Defense cuts on that scale "would have a profound impact on our industrial base," he said.
The country's jobless rate is now at 9.1 percent.
Little said automatic budget cuts would drastically shrink the armed forces as the country wages a major ground war in Afghanistan.
"We'd be looking at, in all likelihood, the smallest Army and Marine Corps in decades," Little said, without providing detailed figures.
The automatic cuts would result in "the smallest tactical Air Force" since it was established in 1947 and "the smallest Navy in nearly a 100 years," he said.
That outcome "would break faith with those in uniform who are serving. At a time of war, that's unacceptable," he said.
The congressional "supercommittee" tackling government spending was created as part of a hard-fought deal signed in August to raise the US debt ceiling.
The US military has a budget of nearly $700 billion, by far the largest in the world.