Speaking earlier on Friday, Mr Biden joked about the way his age was reported in the press.
“They say I’m naive even though I’ve been around 270 years,” he said.
“For the longest time I was too young, because I was the second youngest man ever elected to the United States Senate, and now I’m too old.”
“We gotta finish the job,” he added. “I promise you I am OK.”
HIs gaffes on Thursday were largely reported sympathetically in the US media, and he was praised for his responses to foreign policy questions.
The lead headline on the Washington Post website on Friday morning read: “Biden shows foreign policy depth in news conference with a few stumbles”.