The effort to stabilize and rebuild Afghanistan will be lengthy, complicated and expensive, government watchdogs said Wednesday in a sobering assessment of the challenges facing the Obama administration.

Quelling the growing insurgency is a critical first step before progress can be made rebuilding the country, they said at a congressional hearing, citing the hard lessons in Iraq.

President Barack Obama is expected to disclose a new Afghanistan strategy on Friday that will emphasize more U.S. troops and civilian officials and increased aid to combat militants.

"Unless the expanding Afghanistan program draws upon the lessons learned in Iraq, substantial waste of taxpayer dollars will occur," Stuart Bowen, the special inspector general for Iraq reconstruction, told the House Armed Services Committee.

Arnold Fields, the special inspector general for Afghanistan reconstruction, indicated the U.S. has gotten little return from the $32 billion it has spent over the past seven years, including money to train and equip Afghanistan''s military and police.

Afghanistan lacks Iraq''s infrastructure and oil revenue, which limits the pace and scope of reconstruction projects the U.S. and its allies can pursue, said Fields, a retired Marine Corps general who was appointed last year.

"Iraq had much more upon which to build," Fields said. "We are really constructing as opposed to reconstructing in Afghanistan."