The "dysfunction" in the US Congress, where Republicans and Democrats have failed to compromise on debt reduction, threatens US national security, according to Defense Secretary Leon Panetta.

"One my greatest concerns as secretary is the dysfunction that we see in Washington," he said late Thursday at a ceremony in which he received an award for public service.

"It threatens our security and it raises questions about the capacity of our democracy to respond to crisis."

He went on to express concern over a round of automatic defense spending cuts set to take effect in January 2013 in the event that feuding lawmakers are unable to hammer out a deal to slash the country's $15.8 trillion debt.

"It will force the Department of Defense to throw our new defense strategy out the window. It will pose, I believe, an unacceptable risk to our ability to defend the country," Panetta said.

If Congress fails to agree on how to slash spending by January, dramatic defense reductions of about $500 billion would be automatically triggered under a law adopted last year.

Bitterly divided legislators have been struggling for the past year to reach a deal to rein in the debt, with Republicans demanding steep cuts in spending and Democrats calling for higher taxes on the wealthy.

The looming election-year showdown comes as President Barack Obama, a Democrat, fights for a second term in a campaign dominated by fears over the sluggish US economic recovery.