Former Vice President Joe Biden 'not closing the door' on 2020 presidential run

"But who knows what the situation is going to be a year and a half from now?"

"I'm not closing the door. I've been around too long," he said on NBC News' "Today" show. "I'm a great respecter of fate."

Biden added, "But who knows what the situation is going to be a year and a half from now? I don't have any idea."

Joe Biden announced in 2015 that he would not seek the presidency because the "window on mounting a realistic campaign" closed before his family was able to work through their grief.

"Unfortunately, I believe we're out of time, the time necessary to mount a winning campaign for the nomination," Biden said in October 2015, five months after his son's death.

Asked today by NBC News whether his age would be a problem for voters if he mounts a 2020 campaign, Biden said, "I think it's a legitimate issue for people to raise."

"I do think there's things that [Trump is] doing well," Biden said. "It's more the tone of this administration that bothers me."