Former Vice President Joe Biden said Thursday that he won’t promise to serve just one presidential term because of his advanced age but pledged that he would not seek a second if he loses “energy and mental acuity.”

“Look, I guarantee you this: if anything changed in my health making incapable for me to fully exert all the energy and mental acuity that was needed to be done, I give you my word I would not run again,” Biden, 77, told a CNN town hall.

“It’s totally legitimate for y’all to ask about my age or anybody else’s age up there and our health. That’s why I give all my medical records, everything, okay, the whole deal, so you know where I am,” he said.(RELATED: Joe Biden Interrupts His Wife’s Campaign Speech To Bite Her Finger)

The Democratic presidential candidate continued by saying it is bad policy to publicly state if you don’t plan to run again because you are “already behind the eight ball because then you’re a one-term president and no one worries about what the hell is going to happen after that, okay?”

Biden then observed that he was not the only candidate on stage who was “over 70 years of age. And I’m in pretty good health: knock on wood, as my mother would say.”(RELATED: Joe Biden Stumbles Over His Words In Iowa Speech)

But Biden’s behavior and apparent confusion on the campaign trail has attracted queries about his age and health. He has forgotten where he is at times during speeches, he’s been involved in angry confrontations with potential voters and even called a young woman a “lying, dog-faced pony soldier.” The student at the end of that insult described Biden’s remarks as “tasteless and very sad.”

The former vice president claimed that age should not be the deciding factor when electing a chief executive. “That’s why it’s going to be so important … whoever wins that [voters] pick someone who is ready to be president of the United States on day one. And by the way … it’s totally legitimate to ask about age, because when I ran [for Senate] as a 29-year-old kid, the question was, was I old enough.”

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Biden was the early front-runner in his party’s presidential contest but has struggled in the initial Democratic primaries agains his opponents.