Presumptive Democratic presidential candidate Joe Biden blasted President Donald Trump and denounced "systemic racism" Monday as he sought to reignite his White House campaign after weeks of coronavirus sequestration.

Biden, who had met with anti-racism protesters on Sunday, took to Twitter to express his fury at his opponent's response to the protests that have broken out nationwide over the death of George Floyd, an unarmed black man, at the hands of a white Minnesota police officer.

"He's using the American military against the American people," Biden tweeted after the president vowed to order an army crackdown on civil unrest gripping the United States.

"He tear-gassed peaceful protesters and fired rubber bullets. For a photo," Biden wrote, referring to Trump's decision to use law enforcement -- including military police to clear protesters from outside the White House so he could pose for photographs at a riot-damaged church nearby.

"For our children, for the very soul of our country, we must defeat him," the former vice president said.

Biden also announced in a campaign statement he would speak Tuesday morning in Philadelphia "on the civil unrest facing communities across America."

The speech will be just his third public appearance since the COVID-19 pandemic began in mid-March.

After facing accusations that he was out of touch by spending too much time at home in virus lockdown, the 77-year-old Biden seems to have gotten another wind and is ready to step up the pace of his campaign as restrictions relax.