"To evidence surprise indicates that we didn't have a lot of confidence in our plan," the four-star general said in an interview published Wednesday in the St. Petersburg Times.
"I think the president had confidence in it, the secretary (of defense) had confidence in it, I had confidence in it and our confidence was sort of reinforced when these things came apart the way they did," he said.
He said planning was based on the sequence of events rather than a time-line, under which they would do something for a while and when time was up switch to something else. He said they planned to do something until it was successful and then go on to the next step.
He said they started by working on the air defense system, early warning radar and tanks.
He said they were going to "work on those until we take them out of order so that we can then begin to own the airspace over Afghanistan.
"And so, in the sense that this has been an event-based plan, it really has not been surprising," Franks said.
Franks, 56, is commander of the U.S. Central Command based at MacDill Air Force Base in Tampa, Fla. As Centcom commander he is in charge of the military operation in Afghanistan.
His current task is to take down the al Qaida organization and its leader, Osama bin Laden.
He said because bin Laden heads the al Qaida organization he becomes a target, but not the primary target.
He also said it makes little difference how bin Laden is taken, dead or alive.
"Gosh, I don't know. Justice to him or him to justice. And honestly, either one works well for me. And so, actually, I don't have a preference," Franks said.
"What we want to do is take down the network and the reason we want to take down the network is so that we don't go through more 9-1-1s," he said.
"The cadre of that network happens to be in Afghanistan, but the reach of several of these networks around the planet is just tremendous, and so we have a lot of work to be done and not just in Afghanistan," Franks said.
"And I think it'll take much longer to solve that problem than it will for us to solve the problem in Afghanistan," he said.
Franks said he is aware of the pressure on him to succeed. It is no greater or less than it was immediately after the terrorist attacks Sept. 11, and he tries not to let it bother him.
"You simply don't find a release from it," he said. "I just take a great solace in the fact that I am comfortable with myself, I'm comfortable with my family and that's release enough. So I don't feel overly stressed in the thing. I get enough rest. I get enough exercise and I have an awful lot of great people who work around me."