Trump told reporters during his daily briefing at the White House that he spoke with Biden for about 15 minutes over the phone and the former vice president had offered some "suggestions" on how to better respond to the worsening Covid-19 pandemic.

"We had a really wonderful, warm conversation," Trump said.

"He gave me his point of view and I fully understand that and we had a very friendly conversation. ... It was really good. It was really good. I appreciate his calling."

Trump infamously tried to pressure Ukraine's president into launching an investigation of Biden over baseless corruption allegations last year - a request that resulted in his impeachment.

Still, Trump claimed he doesn't really know anything about Biden.

"I've always thought he was a nice man. I don't know him," Trump said.

Biden, the front-runner for the Democratic nomination to take on Trump in November, did not immediately offer his take on the conversation with Trump.

Kate Bedingfield, Biden's deputy campaign manager, said the two men had a "good call."

Before the call with Trump, Biden was less polite.

"We need a president who actually listens to the experts and heeds their advice," Biden posted, along with a link to a news story on how he plans to wear a face mask in public while Trump has made it clear he won't.

Trump's upbeat comments about Biden came as the US coronavirus death toll surged above 10,000, with more than 360,000 confirmed cases.

Australian Associated Press