EXCLUSIVE: Trump accuses Biden of lying about Obama's lack of endorsement

President TrumpDonald John TrumpTrump conversation with foreign leader part of complaint that led to standoff between intel chief, Congress: report Pelosi: Lewandowski should have been held in contempt 'right then and there' Trump to withdraw FEMA chief nominee: report MORE on Monday accused former Vice President Joe BidenJoe BidenBiden lead shrinks, Sanders and Warren close gap: poll Biden allies: Warren is taking a bite out of his electability argument Budowsky: Donald, Boris, Bibi — The right in retreat MORE of lying about his lack of a 2020 endorsement from former President Obama in an exclusive on-camera interview with Hill.TV.

"How he doesn’t get President Obama to endorse him — there has to be some reason why he’s not endorsing him," Trump said outside the Oval Office. "He was the vice president. They seem to have gotten along. And how President Obama's not endorsing him is rather a big secret," Trump mused, adding, "Then he goes and lies and said, 'I asked the president not to endorse me.' Give me a break."

Trump argued Biden made the assertion because "he’s embarrassed by the fact that Obama’s not endorsing him, so he goes out and says, 'I asked President Obama not to endorse me.' ... So it could be that President Obama knows something, but there is something going on in that brain of his."

Pressed on what exactly is going on in Biden’s brain, Trump said, "I think he’s off. He’s different. We’ve all known him a long time. I’ve seen him for a long time. Frankly, he looks different, he sounds different, and he thinks different. Other than that, I hope he does very well."

Trump in a recent interview with "Fox & Friends" declined to endorse his own vice president, Mike PenceMichael (Mike) Richard PenceBillionaire to host top-dollar fundraiser in New York City for President Trump Poll: Trump neck and neck with top 2020 Democrats in Florida Trump fires back at Graham over Iran criticism MORE, ahead of a possible run for president in 2024. Asked about his comments by NBC News's Chuck ToddCharles (Chuck) David ToddBooker dismisses early surveys: 'If you're polling ahead right now, you should worry' O'Rourke's debate moment reignites gun debate on Sunday shows Liz Cheney says world is more stable, 'safer' under Trump MORE, Trump said he didn't answer because it was a "surprise question."

"I mean it's so far out. That would be the only reason. Now what happens in 2024 I don't know that Mike is going to run. I don't know who's running or anything else," the president said.