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Former Vice President Joe Biden on Monday said he isn't ruling out a run for the Oval Office in 2020, but added he could not accept the nomination if it was given to him right now.

During an appearance on TODAY, Biden said that he's currently focused on promoting his new book, "Promise Me, Dad: A Year of Hope, Hardship, and Purpose," but said he's not ruling out a run completely.

"No, I'm not closing the door. I've been around too long, and I'm a great respecter of fate, but who knows what the situation is going to be a year-and-a-half from now," Biden said.

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He added that while he's currently in good health, he "honest to God" doesn't know if he'll join the race.

On Sunday night, while with TODAY's Matt Lauer, Biden asked a crowd in an Irish pub what they thought of a potential 2020 run. His question was met with raucous applause.

"I was joking," Biden laughed when Lauer brought the moment up on Monday.

Biden has fielded questions about a potential run since last year when he said he could have beaten Donald Trump in the 2016 election.

Related: Biden Book Looks Back at the Path He Didn’t Take (but Still Could)

"The polling data at the time said 'yes,' and since then, but I wasn't in the race. You've got to be in the race. It's a tough game," Biden told TODAY.

The former vice president also addressed controversies in a book by Donna Brazile, the former interim chairwoman of the Democratic National Committee, in which Brazile said she considered replacing Hillary Clinton with Biden in the 2016 election after Clinton fainted.

"The first time I or my staff heard anything about that was in the book, number one. Number two, I wouldn't have taken it," Biden said. "I was for Hillary."

Biden said he had confidence Clinton would have been a "first-rate president," and said at the time he was "not ready, in terms of my family" to take on a presidential campaign.

Biden's new book, published by Flatiron Books, is due to be released on Tuesday.