By Jeffrey Sparshott

The U.S. could face 15% to 18% unemployment and a decline in economic output of up to 9% if political leaders in the coming years don’t make cuts to spending and slash the national debt, according to Sen. Tom Coburn(R., Okla.).

“I think you’ll see the middle class just destroyed if we don’t do this,” Mr. Coburn said on “Fox News Sunday.”

Mr. Coburn said international confidence in the U.S. economy and currency would be undermined if the nation doesn’t start down a road to austerity within three to four years.

The senator was a member of the White House debt-reduction panel and voted in favor of its plan released early this month to cut $4 trillion in debt. That bothered some conservatives because the plan includes ways to increase tax revenues as well as spending cuts.

Mr. Coburn on Sunday said he hopes President Barack Obama and Republicans in Congress can work together next year on $100 billion to $200 billion in cuts that would be a “down payment” on slashing the debt.

While some economists say it’s too soon to talk spending cuts with the economy still weak, Mr. Coburn disagreed. “My hope is that [Mr. Obama] gets out, holds hands with us, and we make some significant cuts,” he said. “There doesn’t have to be a standoff. What there has to be is real leadership and recognizing the serious nature and the urgency of our problem.”