The number of Iraqi army battalions judged by their American trainers to be capable of leading the fight against the insurgency has grown by nearly 50 percent since last September, but the number operating with no U.S. help has slipped from one to none, senior Pentagon officials said Friday.

The U.S. military says its short-term goal is to get more Iraqi units trained to a level where they can lead the fight, since that allows American troops to focus on other tasks besides combat. But in the longer run the Iraqis will have to reach a level of full independence in order for American troops to leave the country.

In a report to Congress assessing the Iraq situation, the Pentagon also asserted Friday that the insurgency is losing strength, becoming less effective in its attacks and failing to undermine the development of an Iraqi democracy.

The report was written last week, before the bombing of a Shiite shrine and a wave of deadly reprisal attacks. It is the third in a series of reports that Congress requires from the Pentagon every three months.

Much of Congress' interest in the military situation in Iraq has focused on the readiness of Iraqi security forces to take over the fight against the insurgency, so that U.S. forces eventually can withdraw from the country.

When Gen. George Casey, the top U.S. commander in Iraq, told the Senate Armed Services Committee last September that the number of Iraqi battalions capable of fighting independently of U.S. troops had dropped from three to one, the news triggered an uproar among Democrats arguing for an early exit from Iraq.

In its report to Congress Friday, the Pentagon did not mention how many Iraqi battalions are rated "Level 1" — those judged to be fully independent. It focused on those at "Level 2," which describes those battalions capable of taking the lead in combat against the insurgents, with some U.S. help. Units at "Level 3" are fighting alongside U.S. forces but are not ready to take the lead in planning and execution of missions.

In a briefing for reporters, Lt. Gen. Gene Renuart disclosed that the number of battalions at Level 1 had dropped from one to zero, while the number at Level 2 had grown from 36 last September to 53 now. He said he did not know precisely why that one battalion had been downgraded, but he said it reflected the general inadequacy of the Iraqi defense forces' ability to provide their own transport and logistical support.

"What you will start to see, I think, as we get in past the April or May timeframe is an increasing number of Iraqi battalions" with enough of a support system to allow them to be upgraded to Level 1, Renuart said.

The total number of Iraqi security forces is now about 232,000, according to Peter Rodman, the assistant secretary of defense for international security policy, who joined Renuart in briefing reporters after the pair reviewed the Iraq report with congressional staffers.