Donald Trump had an epic tantrum when a journalist asked him if he would concede the election he lost earlier this month.
The US president branded Reuters White House correspondent Jeff Mason a "lightweight" during a Thanksgiving briefing at the White House.
Trump was asked if he would concede the election once the Electoral College formally votes to make Joe Biden the next president of the United States.
He avoided the question and said it would be "a mistake" if the Electoral College confirmed Biden will be the next president.
Trump repeated his claims of fraud during the election despite having no proof of it.
As Mr Mason tried to get the US president to answer the question he asked, Trump told him in an epic tantrum: "Don't talk to me that way.
"You're just a lightweight. Don't talk to me that way."
Pointing his finger towards the journalist, Trump added: "I'm the president of the United States.
"Don't ever talk to the president that way."
He then moved on to a different journalist for another question.
The reporter asked him whether he would not leave the White House when the Electoral College votes Joe Biden as the next president.
Trump replied: "Certainly I will, certainly I will. And you know that."
But shortly after the news conference, during which he seemed willing to concede when Biden is certified the winner, Trump tweeted that he "won" the election.
The president has previously clashed with Mr Mason and mocked him in September when the journalist refused to take off his face mask when asking a question.
After their clash on November 26, Mr Mason did not comment, but only tweeted some key points from the news conference.
In one tweet, he wrote: "Trump says if the Electoral College votes for Biden it would be a mistake, but says he will leave the White House if it does."
In another one, he added: "Trump says he does not want to say yet whether he would attend the inauguration of Joe Biden."
The reporter also tweeted a photo of the US president, with the caption: "Don’t let Joe Biden take credit for the vaccines, @realDonaldTrump says."
Joe Biden won the US presidential election on November 3 with 306 Electoral College votes - many more than the 270 needed for victory - to Trump's 232.
Biden also leads by more than six million in the popular vote tally, with a record number of votes won.
The Trump campaign is still expected to mount a legal challenge to the overall result in Wisconsin, but time is running out as the state is due to certify its presidential result on Tuesday.
