Defense Secretary Robert Gates said the military can focus more attention on Afghanistan because of improved security in Iraq.
The comments come one day after President Bush announced a plan to withdraw about 8,000 troops from Iraq by early next year.
Gates also testified to the House Armed Services Committee that troops should be withdrawn slowly and that Americans should expect to be involved there for many years to come.
"I worry that the great progress our troops and the Iraqis have made has the potential to override a measure of caution born of uncertainty," Gates said.
"Our military commanders do not yet believe our gains are necessarily enduring - and they believe that there are still many challenges and the potential for reversals in the future."
Gates also warned that "we should expect to be involved in Iraq for years to come, although in changing and increasingly limited ways."
The Defense secretary said sectarian tensions still exist in Iraq and have the potential to undo recent security progress.
Meanwhile, President Bush is meeting with the Iraqi president today to discuss legislative issues in Baghdad.
Source: CBN News, The Associated Press