Presumptive Democratic presidential nominee Joe Biden on Wednesday fired back after President Trump complained that Biden's running mate, Senator Kamala Harris (D-CA), was "nasty" to Supreme Court Justice Brett Kavanaugh.

"Donald Trump has already started his attacks, calling Kamala 'nasty,' whining about how she's 'mean' to his appointees," Biden said at a campaign event to introduce Harris as his running mate.

"It’s no surprise because whining is what Donald Trump does best, better than any president in American history," Biden said. "Is anyone surprised Donald Trump has a problem with a strong woman or strong women across the board?"

Biden on Tuesday announced that he had chosen Harris as his running mate, fulfilling a commitment the former Vice President made in March to name a woman as running mate.

Trump, in his first public comments after Harris was announced as the Democratic vice presidential candidate, mentioned Harris' questioning of Kavanaugh during a Senate Judiciary Committee hearing in 2018.

"She was extraordinarily nasty to Kavanaugh — Judge Kavanaugh, then; now Justice Kavanaugh," Trump said during a press briefing. "She was nasty to a level that was just a horrible thing. The way she was — the way she treated now-Justice Kavanaugh. And I won't forget that soon."

Trump also said Harris had been “very, very nasty” to Biden during the primaries.

“One of the reasons that it surprised me, she was probably nastier than even Pocahontas to Joe Biden. She was very disrespectful to Joe Biden and it’s hard to pick somebody that that’s disrespectful,” he told reporters. “Pocahontas” is a reference to Senator Elizabeth Warren.