Financial analysts are cutting back their earnings estimates for America's biggest businesses, down to the lowest levels since the financial crisis began in 2008.

Analysts are responding to indicators that the U.S. economy is slowing again. Some believe the United States may already be in a recession.

"Revenue estimates for the back half of 2012 have been slowly working their way lower this year," Nicholas Colas, chief market strategist at ConvergEx in New York, said.

"This trend, however, has accelerated to the downside over the past 30 days and we are fast approaching levels where these estimates are unambiguously pointing to the risk of a U.S./global recession later into 2012 and 2013," he said.

Much of Europe is already in a recession and other economic powers, like China, India, and Brazil, are also slowing down.

Analysts only expect revenue to grow at just 1 percent to 1.5 percent pace in the third quarter.