President George W. Bush admitted on Thursday his troop buildup in Iraq had made limited progress but said he would wait for a September security report before considering a change of course.

An interim White House report found the Iraqi government had made only mixed progress in meeting political goals. It said conditions were still dangerous and challenging, six months after Bush ordered a U.S. troop buildup.

Bush said it was too early to evaluate whether the troop increase was working and that a broader assessment by Gen. David Petraeus and U.S. Ambassador Ryan Crocker in September will be pivotal.

We'll ... have a clearer picture of how the new strategy is unfolding, and be in a better position to judge where we need to make any adjustments, Bush told a news conference.

The report is being sent to Congress as several prominent Republicans have broken ranks with Bush on Iraq to urge a shift in policy.

The Republican revolt could accelerate Democratic-led efforts to try to force Bush to start scaling back troop levels in Iraq more than four years after a U.S.-led invasion that toppled Saddam Hussein.

Those who believe that the battle in Iraq is lost will likely point to the unsatisfactory performance on some of the political benchmarks, Bush said. Those of us who believe the battle in Iraq can and must be won see the satisfactory performance on several of the security benchmarks as a cause for optimism.

The interim report showed limited progress by the Iraqi government in meeting goals for political reconciliation such as passing a law to share oil revenues.

It also warned of the risk of further attacks by al Qaeda in coming months.

The security situation in Iraq remains complex and extremely challenging, the report said.

Drafted by White House officials with leading contributions from Petraeus and Crocker, the report echoed recent comments from Bush saying it is hard to gauge progress in Iraq less than a month after all of the additional 28,000 U.S. troops have arrived in Iraq.

A USA Today/Gallup poll this week showed more than seven in 10 Americans favor withdrawing nearly all U.S. troops by April. Several surveys show Bush's approval ratings are at the lows of his presidency.

(Additional reporting by Matt Spetalnick

Iraq George W. Bush