Without a deal, tax cuts from 2001 and 2003 -- when George W. Bush was president -- will expire, raising rates for everyone starting in January. In addition, spending cuts would reduce spending on the military, national parks, the Federal Aviation Administration and other government services.

However, the government and Congress still would have time to prevent draconian effects from the fiscal cliff when a new Congress convenes in January.

William Galston, a senior fellow in governance studies at the Brookings Institution, called that a form of brinksmanship best avoided.

"To be sure, no one believes that non-agreement by December 31 would be the end of the story. After a period of finger-pointing, discussions would resume," he wrote last week in a New Republic opinion piece. "But equally, no one knows how the failure to reach agreement before the end of 2012 would affect the dynamics of the negotiations."

In addition, "we can be reasonably sure ... that national and global markets would react adversely and that businesses, which are already retreating from planned investments in new plant and equipment, would become even more uncertain and risk-averse."