WASHINGTON — Defense Secretary Robert Gates said Thursday he has abandoned hope that troop levels in Iraq will drop to 100,000 by the end of the year.

Instead, he told a Senate panel that he expects that Gen. David Petraeus, the top military commander in the war, will be able to make an assessment of further drawdowns by mid-September.

Last fall, the secretary said he held out hope that troop levels in Iraq could continue to drop through this year. While he would not put a specific number troop levels, he agreed at the time that a consistent reduction would have left about 10 brigades — or roughly 100,000 troops — by the end of the year.

When asked by Sen. Carl Levin, chairman of the Armed Services Committee, if that remains his hope, Gates responded: "No sir."

However, Gates took a somewhat different tone than Petraeus and even President Bush by describing plans to halt troop withdrawals this summer as a "brief pause." Petraeus and Bush have rejected that description.

Gates said he decided to use the term anyway in congressional testimony because he expects that Petraeus will be able to make an assessment come September.

"If the conditions continue to improve in Iraq, as we have seen them improve over the last 14 or 15 months, than we believe the circumstances are in place for him to be able to recommend continuing drawdowns," Gates said. "But I think while we have used different words, that certainly is my understanding and my expectation."

Petraeus has recommended, and Bush has agreed, to complete the pullout of 20,000 troops by July but also to halt further reductions after that. Petraeus has said he needs a 45-day period of evaluation, to be followed by an indefinite period of assessment before he would recommend any further pullouts.

In two days of congressional testimony, the four-star general repeatedly refused to answer questions by lawmakers wanting to know how long the assessment period will last.

"It's when the conditions are met that we can make a recommendation for further reductions," Petraeus told Levin on Tuesday.

Bush, who has embraced Petraeus' recommendation, also has not said how long it might be before more troops can come home. In a speech on Thursday, just hours before Gates testified, Bush specifically rejected the term "pause" as misleading "because none of our operations in Iraq will be on hold."

When Levin asked Gates why he would use the term "pause" when Petraeus refused, Gates responded: "One of the benefits of being the secretary of defense, I suppose, is that I'm allowed more to hope than the field commander is."