Iraq Progress 'Fragile and Reversible' After Bombings, Petraeus Warns

Progress in Iraq is still "fragile and reversible," Gen. David Petraeus warned Friday after back-to-back homicide bombings killed nearly 80 people one day earlier in Iraq's deadliest day in more than a year.

But the U.S. military is nevertheless set to withdraw from the war-torn country on schedule, he told a House appropriations subcommittee.

Petraeus, the head of U.S. Central Command, addressed the lingering extremist threat in Iraq as he outlined his approach to the escalating campaign against extremists in Pakistan and Afghanistan.

"There has ... been substantial progress in Iraq, but numerous challenges still confront its leaders and its people, and we have seen some of those in the last couple of days," Petraeus said. He said Al Qaeda in Iraq and other extremist groups still threaten security and stability in the country.

Those challenges, combined with ethnic and political tensions and other problems, "remind us that the progress there is still fragile and reversible, though less so than when I left Iraq last fall," Petraeus said.

Nonetheless, he said, coalition forces are making progress transferring security responsibility to Iraqi forces, allowing for a steady withdrawal of U.S. units from urban areas. He said the military is on track to fulfill President Obama's long-term strategy.

The president has called for the U.S. combat mission to end by Aug. 31, 2010, with a residual force of up to 50,000 to remain through the following year.