Democratic presidential candidate Joe Biden is holding his first campaign event with Kamala Harris, a day after unveiling her as his running mate.
At a high school in Mr Biden’s home state of Delaware, he said “this is a serious moment for our nation” ahead of November’s election.
Later on Wednesday, they will hold a virtual town hall from the hotel where Mr Biden launched his 1972 senate bid.
Mr Biden will face President Donald Trump in the election on 3 November.
Ms Harris, a California senator, is the first black woman and South Asian American to serve in the role.
What did the candidates say?
Wednesday’s event in Wilmington, Delaware, was not open to the public, with Mr Biden citing coronavirus prevention needs. both candidates walked on stage wearing masks.
Speaking from the gymnasium of the Alexis I DuPont High School to a socially distanced group of journalists, 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?”
What is President Trump saying?
Shortly before the event, Mr Trump goaded Mr Biden for remaining at home for much of the campaign so far amid the pandemic lockdown.
The Republican president asked a group of teachers at a White House event; whether it was healthy for students to be learning in isolation at home.
He then asked: “So if you’re a presidential candidate; and you’re sitting in a basement
and you’re looking at a computer, that’s not a good thing?”
He also tweeted an attack on the Biden-Harris ticket; saying they would put Senator Cory Booker, who is black, in charge of low-income housing in the suburbs.
Critics said the tweet was racist.