The U.S. military has stopped announcing its plans for turning over facilities to the Iraqi government because of concerns that insurgents were using the information to stage attacks, a top American general said Thursday.

“As bases close, some adversaries try to take advantage and attack us. . . . Some attacked on transition day,” Maj. Gen. Thomas W. Spoehr, deputy commanding general of U.S. Forces-Iraq, said during a telephone news conference from Iraq.

Spoehr said the departure schedule, which once was publicized to assure the Iraqi public about the U.S. troop withdrawal , is now kept “under wraps.”

The U.S. military once occupied more than 500 bases in Iraq. It now has 22. The Iraqi military controls most former U.S. bases.

U.S. officials also have been negotiating with Iraqi leaders over how many, if any, troops will remain after the Dec. 31 deadline for withdrawing U.S. forces. Any who remain behind, likely in the vicinity of 5,000 troops, would be trainers for Iraqi forces. There are several potential sticking points, including whether U.S. military personnel would continue to be immune from Iraqi laws after the end of the year.

After eight years of conflict, about 41,000 U.S. troops are in Iraq, but almost all will be gone by mid-December, Spoehr said . Most of those left are engaged inforce protection. “There is constant concern of enemy attacks,” he said.

Spoehr said the removal of troops, equipment and property from Iraq is the most complex logistics problem handled by the military since World War II.

Last week, for example, it took 13,900 trucks in 399 convoys to move equipment, fuel and food in and out of Iraq, according to Maj. Gen. Jeffrey S. Buchanan, the chief spokesman for U.S. forces in Iraq. Spoehr said that, on average, some 520 soldiers are leaving every day.

He said that about 25,000 pieces of equipment, both military and non-military in nature, have been sold or turned over to Iraq as surplus. In September alone, 1,100 pieces of heavy equipment, much of it for construction, have been deemed excess to military needs and sold at discount prices to U.S. states. About 23,000 U.S. military vehicles remain in Iraq.

Spoehr said that it costs about $40,000 to ship a 40-foot container back to the United States, and that has encouraged the military to leave material in Iraq. He said that some 142 million pounds of equipment had been sold as scrap over the past year, 6.8 million pounds in September alone.

He also said the military has used sophisticated methods in packing up. Containers are filled with similar items and each are given an electronic tagthat, using radio signals, identifies its contents to computers tracking the shipments.