The White House announced Monday that Gen. David H. Petraeus, top military commander in Iraq, and U.S. Ambassador Ryan Crocker will testify before Congress in open hearings ahead of the formal Sept. 15 deadline for a new progress report on the war.

Spokesman Gordon Johndroe said Petraeus and Crocker will probably appear before the relevant Senate committees on Sept. 11 and 12. Congress recesses for the week at the start of Rosh Hashanah at sunset Sept. 12.

The announcement came as Sen. Carl Levin, D-Mich., chairman of the Armed Services Committee, and John W. Warner, R-Va., a former chairman, prepared to brief reporters on their “very productive” two-day trip to Iraq last week to assess progress from the military “surge” that President Bush ordered in January.

The influential senators said “the military aspects of President Bush’s new strategy in Iraq, as articulated by him on January 10, 2007, appear to have produced some credible and positive results.”

But they were less sanguine about the political situation. “While we believe that the ‘surge’ is having measurable results, and has provided a degree of ‘breathing space’ for Iraqi politicians to make the political compromises which are essential for a political solution in Iraq, we are not optimistic about the prospects for those compromises,” the senators said.

Unless the current Iraqi government quickly improves, Levin and Warner said that “we believe the Iraqi Council of Representatives and the Iraqi people need to judge the Government of Iraq’s record and determine what actions should be taken — consistent with the Iraqi Constitution — to form a true unity government to meet those responsibilities.”