Secretary of Defense Robert Gates is warning a failure in Afghanistan would be a 'huge setback for the United States' with 'catastrophic consequences.'

Gates, appearing on CNN's 'State of The Union' Sunday said a victory by extremist forces would only encourage more extremism.

"Failure in Afghanistan wouls be a huge setback for the United States," Gates said. "Taliban and al Qaida, as far as they're concerned, defeated one super power. For them to be seen to defeat a second I think would have catastrophic consequences."

The former Soviet Union was defeated in the 1980s.

Gates said it would be a mistake to set a deadline for withdrawing.

His appearance came as the top commander in Afghanistan is requesting more troops, in addition to the 21,000 President Obama sent shortly after he took office.

General Stanley McChrystal, appearing on '60 Minutes' Sunday night, called for faster progress in Afghanistan.

The 3rd Brigade Combat Team of the 10th Mountain Division is scheduled to remain in Afghanistan until January, and the division's Aviation Brigade is scheduled to go to Afghanistan in the fall od 2010.

- CNN, Associated Press, 7 News staff