Economists lowered their U.S. economic growth outlook for the next two years as they raised their expectations for the unemployment rate, a survey released on Monday showed.

The Philadelphia Federal Reserve's fourth-quarter survey of 45 forecasters showed gross domestic product (GDP) was expected to grow at an average annual rate of 2.4 percent in 2012, down from an estimate of 2.6 percent in the third-quarter survey.

Growth for 2013 was lowered to 2.7 percent from 2.9 percent.

For the current quarter, the growth forecast held steady at 2.6 percent, while the estimate for 2011 was nudged up to 1.8 percent from 1.7 percent.

The outlook for the job market also deteriorated with the unemployment rate expected to average 8.8 percent next year, up from an earlier forecast of 8.6 percent. The outlook for 2013 outlook was lifted to 8.4 percent from 8.1 percent.

Unemployment expectations for the fourth quarter and 2011 overall were unchanged at 9.0 percent for both.

Economists raised their expectations for consumer prices for 2011 to 3.6 percent from 3.2 percent, though 2012's forecast was lowered to 1.9 percent from 2.0 percent.