Up to 3.4 million jobs would be lost, the Congressional Budget Office estimates. The unemployment rate would reach 9.1 percent from the current 7.9 percent. Stocks could plunge. The nonpartisan CBO estimates the total cost of the cliff in 2013 at $671 billion.

Collectively, the tax increases would be the steepest to hit Americans in 60 years when measured as a percentage of the economy.

"There would be a huge shock effect to the U.S. economy," says Mark Vitner, an economist at Wells Fargo.

Most of the damage — roughly two-thirds — would come from the tax increases. But the spending cuts would cause pain, too.

The bleak scenario could push the White House and Congress to reach a deal before year's end. On Tuesday, Congress returns for a post-election session that could last through Dec. 31. At a minimum, analysts say some temporary compromise might be reached, allowing a final deal to be cut early next year.

[link to news.yahoo.com]