WASHINGTON - -Progress will come more slowly from the Afghan troop surge than it did during a similar U.S. escalation in Iraq, the top American commander in the Middle East told Congress on Wednesday, predicting intensified combat in coming months.

Gen. David H. Petraeus, head of U.S. Central Command, said Afghanistan is beset by problems that will challenge the new U.S. strategy, including government corruption, insurgent sanctuaries along the Pakistan border and the strength of the Taliban.

Petraeus commanded U.S. forces in Iraq in 2007 and 2008 and often called the situation in Iraq "hard but not hopeless." Testifying before the Senate Foreign Relations Committee, Petraeus said Afghanistan is "no more hopeless" than Iraq was.

"Achieving our objectives in Afghanistan ... will not be easy," Petraeus said. "The Taliban has in recent years been gaining strength and expanding the extent of its control of parts of Afghanistan."

Petraeus predicted an increase in violence next summer. He also said that as pressure mounts on the Afghan government to fight corruption, political conflicts and other governmental turmoil are likely.