Iraqi security forces who are trained and equipped now number 142,472, defense officials told a House panel Monday.

Congressional investigators criticized the number as unreliable.

"Without reliable reporting data, a more capable Iraqi force and stronger Iraqi leadership, the Department of Defense faces difficulties in implementing its strategy to draw down U.S. forces from Iraq," the General Accountability Office (search), the investigative arm of Congress, said in written testimony.

The Bush administration has said a trained Iraqi security force is the key to the United States' gradual drawdown of its troops because Iraqis then would be able to secure their own country.

Defense officials told a national security panel of the House Government Reform Committee that over time the Pentagon (search) has changed the way it tracked the number of trained Iraqi security forces.

Since September, the tally has included only those who have both the training and equipment to engage in combat. Before, the Pentagon had included anyone who was on duty regardless of training.

As of March 7, defense officials said, there were 81,889 trained and equipped police, highway patrol and other forces in the Ministry of Interior Forces (search) and 60,583 troops in the Ministry of Defense Forces.

But the GAO said Monday the number of police forces is unreliable because it includes police who may be absent from duty without authorization. "The Ministry of the Interior does not receive consistent and accurate reporting from the police forces around the country," the GAO written testimony said.