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.
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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.
"Is anybody surprised that Donald Trump has a problem with a strong woman, or strong women across the board?"
He also attacked Mr Trump's handling of the coronavirus pandemic, climate change, the unemployment rate and "his politics of racist rhetoric that appeals to division".
What did Harris say?
Coming to the podium next, Ms Harris said: "I am ready to get to work."
The 55-year-old former prosecutor told reporters: "Everything we care about, our economy, our health, our children, the kind of country we live in, it's all on the line."
Ms Harris - the daughter of immigrants from India and Jamaica - continued: "America is crying out for leadership, yet we have a president who cares more about himself than the people who elected him.
"He inherited the longest economic expansion in history from Barack Obama and Joe Biden. And then, like everything else he inherited, he ran it straight into the ground."
Source: BBC