WASHINGTON -- A comprehensive strategy in Afghanistan -- including an exit plan -- is key to America's "No. 1 mission" of preventing an attack on the U.S., its interests or its allies, President Obama said in an interview broadcast Sunday.

"What we can't do is think that just a military approach in Afghanistan is going to be able to solve our problems," the president said on CBS' "60 Minutes." "So what we're looking for is a comprehensive strategy. And there's got to be an exit strategy. There's got to be a sense that this is not perpetual drift."

Obama's comments were a prelude to a revamped plan for fighting insurgents in Afghanistan and Pakistan, which is expected to be announced this week. On Friday, a military official said the overhauled U.S. strategy would call for new garrisons in far-flung Afghan communities to better hold off the Taliban.

Obama's plan covers the next three to five years, with the goals of containing the insurgency, heading off the possibility that it could topple Afghanistan's fragile central government and providing enough security for Afghan citizens that they reject the insurgents of their own accord, the official said Friday. He spoke on condition of anonymity because the review was not complete.

In the CBS interview, Obama warned that Afghanistan would be "a tough nut to crack," with issues that commanders on the ground judged to be more difficult to resolve than Iraq.

"It's easier terrain," the president said of Iraq, where the war is winding down after six hard-fought years. "You've got a much better educated population, infrastructure to build off of. You don't have some of the same destabilizing border issues that you have between Afghanistan and Pakistan."

Obama said an effective strategy in Afghanistan could include:

-- building economic capacity in Afghanistan;

-- improving diplomatic efforts in Pakistan;

-- bringing a more regional diplomatic approach to bear;

-- and coordinating more effectively with allies.

When asked about the most frustrating part of his job, Obama took a jab at his predecessor, George W. Bush.

"You are often confronted with bad choices that flow from less than optimal decisions made a year ago, two years ago, five years ago, when you weren't here," Obama said. "A lot of times, when things land at my desk, it's a choice between bad and worse."

He again took issue with former Vice President Dick Cheney, who criticized the Obama administration for shutting down the Guantanamo Bay detention center and forbidding torture of terrorist suspects. Cheney said such steps are making America weaker and more vulnerable to attack.

"The facts don't bear him out," Obama said. "Let's assume we didn't change these practices. Are we going to just keep on going until ... the entire Muslim world and Arab world despises us? Do we think that's really going to make us safer? I don't know a lot of thoughtful thinkers, liberal or conservative, who think that that was the right approach."

In the interview, Obama said the most difficult decision he's had to make in his 2-month-old presidency was to send more troops to Afghanistan, which he decided before completion of a strategic review on the region.

"When I make a decision to send 17,000 young Americans to Afghanistan, you can understand that intellectually, but understanding what that means for those families, for those young people when you end up sitting at your desk, signing a condolence letter to one of the family members of a fallen hero, you're reminded each and every day at every moment that the decisions you make count."