US President Joe Biden warned his staff in the White House that they must show respect to their colleagues, or else "I will fire you on the spot", Axios news portal reported.
"I'm not joking when I say this: If you're ever working with me and I hear you treat another colleague with disrespect, talk down to someone, I promise you I will fire you on the spot," he added. "On the spot. No ifs or buts".
The White House had been largely emptied of staff after Trump flew to Florida on Wednesday as he had decided against attending his successor's inauguration.