"I think it's a stretch to, in any way, to say that she's got the experience to be president of the United States," Mr Hagel told the Omaha World-Herald newspaper.
And he was dismissive of the fact that Mrs Palin, the governor of Alaska, has made few trips abroad.
"You get a passport for the first time in your life last year? I mean, I don't know what you can say. You can't say anything."