Democratic presidential candidate Joe Biden and running mate Kamala Harris have attacked "whining" President Donald Trump as an incompetent leader who has left the US "in tatters".
The pair held their first campaign event together, a day after Mr Biden unveiled Ms Harris as his number two.
President Trump hit back, saying Ms Harris had "dropped like a rock" in her own presidential bid.
Mr Biden will face Mr Trump, a Republican, in November's election.
What did Biden say?
Wednesday's event at a school in Wilmington, Delaware, was not open to the public, with Mr Biden, 77, citing coronavirus prevention needs. Both candidates walked on stage wearing masks to address a group of masked journalists.
Mr Biden noted that Ms Harris, a US senator from California, was the first woman of colour to serve as a presidential running mate for a major US party.
Mr Biden said: "The choice we make this November is going to decide the future of America for a very, very long time."
He continued: "Donald Trump has already started his attacks, calling Kamala, quote, nasty, whining about how she is, quote, mean to his appointees.
"It's not a surprise because whining is what Donald Trump does best, better than any president in American history.