The Pentagon (search) told Congress Thursday that Iraqi insurgents are failing to derail the move toward democracy but remain "capable, adaptable and intent" on carrying out lethal attacks aided by a continuing inflow of foreign terrorists.

Its 23-page report — the most comprehensive public assessment yet by the military establishment of progress in Iraq — was more than a week overdue. In it, the Pentagon cited progress on political, economic and security fronts. But it did not say how soon Iraqi security forces would be sufficiently trained to defend the country without the direct assistance of American troops.

U.S. officers have developed a method of calculating the combat readiness of the approximately 76,700 Iraqi Army troops, but the Pentagon said it "should not and must not" publicly disclose specific data.

"The enemy's knowledge of such details would put both Iraqi and coalition forces at increased risk," the report said.

That information, along with details on various possible changes in the level of U.S. forces in Iraq (search) next year, were included in an annex, classified as secret, along with the unclassified report delivered to Congress (search).

There currently are about 138,000 U.S. troops in Iraq. The Pentagon report offered no estimate of when they could be withdrawn.

Democratic critics of Bush administration Iraq policy lashed out at the Pentagon for refusing to publicly release a detailed assessment of the readiness of Iraqi security forces.

Sen. Carl Levin, ranking Democrat on the Senate Armed Services Committee, said he fears "the American people are going to be left out" of discussions about when the United States can bring troops home and turn the wartorn country over to Iraqi security forces.

Last week, Gen. Peter Pace, the vice chairman of the Joint Chiefs of Staff, provided a written statement to the Senate Armed Services Committee that said about half of Iraq's new police battalions are still being established and cannot yet conduct operations. He provided the statement in response to a question posed by Levin.

It was not clear how that squared with an assertion in Thursday's report to Congress that "more than half of provincial police headquarters currently are assessed to have control in their province."

Pace said the other half of the police units and two-thirds of the new army battalions are only "partially capable" of carrying out counterinsurgency missions and need U.S. help.

"Only a small number of Iraqi Security Forces are taking on the insurgents and terrorists by themselves," Pace wrote in the memo.

In a briefing for reporters at the Pentagon, Lt. Gen. Walter Sharp said the insurgents have shifted their focus from attacking U.S. troops to civilian targets. "That's why you are seeing more civilian casualties," he said.

Thursday's report to Congress noted that when U.S. and Iraqi forces assaulted the insurgent stronghold of Fallujah last November several Iraqi battalions "collapsed." Absenteeism among regular Iraqi army units was "in double digits" and remained so for the rest of the year, it added.

"Although such problems have not been entirely solved, they have been addressed in large measure," the report said, due in part to efforts that have alleviated equipment shortages.

"Still, units that are conducting operations and units that relocate elsewhere in Iraqi experience a surge in absenteeism," it added.

Although the report said that Iraqi Sunnis make up the largest proportion of the insurgency, it also decried a continuing influx of foreign terrorists from across Iraq's borders. Iraq has 15,500 trained border police, but their effectiveness varies widely and is rated by U.S. officials as "generally moderate to low."

"Although violent extremist activity accounts for a fraction of the overall violence, the dramatic and symbolic nature and lethality of their attacks, combined with effective information operations, has a disproportionate psychological impact relative to their numbers," the report said.

Outlining the way forward on the political front, the report said that Washington expects the Iraqis to meet an Aug. 15 deadline for writing a constitution, followed by a national referendum on the constitution by Oct. 15 and a Dec. 15 election under that constitution for a permanent government that would take power shortly thereafter.

"One noteworthy strategic indicator of progress toward a stable security environment has been the inability of insurgents to derail the political process and timeline," the report said. "To do so is the strategic objective of the insurgents, and they are failing to achieve it."