Joe Biden and Boris Johnson discuss Covid-19 recovery in a Saturday phone call three days after the inauguration.
The UK prime minister tweeted on Saturday: “Great to speak to President Joe Biden this evening."
Earlier Mr Biden told the US Conference of Mayors that his administration was focussing on the pandemic and economic growth.
“We also have to act now, with urgency and unity as the United States of America…We can do this together. I promise we’ll do everything we can to help," said Mr Biden.
It comes as former Trump administration officials are quietly lobbying congressional Republicans to convict Mr Trump in his impeachment trial next month, according to CNN.
The former officials are just some of the dozens of influential GOP figures in Washington who want the party to sever ties with the former president.