WILMINGTON, DEL. - Presumptive Democratic Party presidential nominee Joe Biden is calling for a national mask mandate to cut the number of future deaths from the coronavirus in the United States.  

"It doesn't have anything to do with Democrats, Republican or independents," Biden said, but "every single American should be wearing a mask when they are outside for the next three months at a minimum."  

Hour later, President Donald Trump accused Biden of politicizing the pandemic with the request, asserting that a mask mandate would cripple the economy, leading to a depression by wanting to "lock all Americans in their basements for months on end."

The former vice president, in Wilmington, said the governors of every U.S. state "should mandate mandatory mask wearing," adding that experts estimate such compliance "will save 40,000 lives in the next three months."    

The Trump administration has repeatedly rejected calls for a national mask mandate, leaving such decisions to state governors.  

"It's not about your rights," Biden said to a group of reporters in his home state of Delaware. "It's about your responsibility as an American. This is America. Be a patriot. Protect your fellow citizens. Step up. Do the right thing."  

The president, at an evening news conference, responded that he had emphasized that wearing a mask is a patriotic thing to do.

"Maybe they're great and maybe they're just good, maybe they're not so good," Trump said of masks. "But frankly what do you have to lose?"

Trump said, however, there is an issue of freedom when it comes to wearing masks - which has become a politically divisive issue in the United States.

"We want to have a certain freedom. That's what we're about," the president said.

Biden's running mate, Senator Kamala Harris of California, said it is important that Americans looking at the upcoming election "ask the current occupant of the White House, 'When am I going to get vaccinated? When am I actually going to get vaccinated?'"  

Most public health officials expect no vaccine ready for mass inoculations in the United States prior to 2021. Trump, however, has spoken of a vaccine possibly being ready by the time of the presidential election in early November.  

Biden and Harris made their remarks inside a luxury Wilmington hotel after receiving two virtual briefings - one on the COVID-19 public health crisis, and the other on the economic downturn.  

The presumptive Democratic Party nominees sat at desks in a hotel ballroom, facing each other without wearing masks but socially distanced. 

The other participants joined via video links, and their faces were displayed on a large screen behind Biden and Harris.  

Among those briefing the candidates about the coronavirus pandemic were Dr. Vivek Murthy, a former U.S. surgeon general, and Dr. Nicki Lurie, a former assistant secretary for preparedness and response at the U.S. Department of Health and Human Services.  

The participants in the economic briefing included Janet Yellen, former chair of the Federal Reserve Board. 

Patsy Widakuswara contributed to this report.