A growing number of Iraqi troop battalions — nearly four dozen as of this week — are playing lead roles in the fight against the insurgency, and American commanders have turned over more than two dozen U.S.-established bases to government control, officials said Monday.

Those are among signs of progress that the Bush administration is citing as evidence that the Iraqis not only want more responsibility on the security front but are capable of handling it with less assistance from U.S. troops.

The steps toward lessening the U.S. military role in Iraq come amid mounting political pressure on the Bush administration to reduce the American presence in the face of rising casualties and an unrelenting insurgency.

President Bush is to give a major speech Wednesday at the U.S. Naval Academy in which administration officials say he is expected to spotlight recent steps toward improving the readiness of Iraqi troops.

There are now about 160,000 U.S. troops in Iraq. They have trained and equipped about 212,000 Iraqi security forces, including infantry, commandos, special police battalions and a variety of military support units. The figure is supposed to reach 230,000 by mid-December and top out at 325,000 by July 2007.

Pentagon officials acknowledge that there are significant gaps in the Iraqis' ability to defend their own country, and they are unwilling to commit to any specific drawdown of U.S. forces next year, beyond the announced plan to pull back 28,000 troops who were added this fall for extra security during the elections.

Many in Congress have expressed worry at what they see as sluggish progress in training Iraqi security forces, even as U.S. commanders insist that measures of progress have been widely misunderstood.

Lt. Col. Fred Wellman, a spokesman in Baghdad for the U.S. command that is responsible for the training and equipping of Iraqi security forces, said Monday that approximately 130 Iraqi army and special police battalions are fighting the insurgency, of which about 45 are rated as "in the lead," with varying degrees of reliance on U.S. support. The exact numbers are classified as secret, but the 45 figure is about five higher than the number given on Nov. 7 at a briefing by Lt. Gen. David Petraeus, who previously led the training mission. And it is about 10 higher than the figure Petraeus offered at a Pentagon briefing on Oct. 5.

An Iraqi battalion usually numbers between 700 and 800 soldiers.

As another measure of progress, Wellman said about 33 Iraqi security battalions are now in charge of their own "battle space," including parts of Baghdad. That figure was at 24 in late October. Wellman said it stood at three last March.

Also, the Americans have pulled out of 30 "forward operating bases" inside Iraq, of which 16 have been transferred to Iraqi security forces. The most recent and widely publicized was a large base near Tikrit, which U.S. forces had used as a division headquarters since shortly after the fall of Baghdad in April 2003.

At a Nov. 22 ceremony marking the Tikrit base transfer to Iraqi control, insurgents delivered a reminder of their resilience by firing a mortar nearby; it failed to explode, and U.S. officials declared the handover to be an important step in replacing U.S. forces with Iraqis.

Lawrence Di Rita, spokesman for Defense Secretary Donald H. Rumsfeld, said Monday that the transfer of authority at formerly U.S.-controlled bases is an important part of the long-range plan for stabilizing the country.

"As you continue to either close or turn over these bases, it's just self-evident that there would be some reduced need for the American presence in those areas," Di Rita said.

The spokesman said no decisions on future troop levels were likely until after the Dec. 15 election of a new Iraqi government. He suggested, however, that signs point to reductions during the course of 2006, so long as the political process remains on track.

Gen. George Casey, the top U.S. commander in Iraq, is continually assessing the security situation, Di Rita said.

"He's presented a variety of alternative approaches that could occur after the election, but again it's all based on waiting to see how it goes and waiting and watching as we continue to hand over responsibility to the Iraqis," Di Rita said.