In front of a crowd, Sen. Bernie Sanders, I-Vt.on Saturday wished President Trump and First Lady Melania Trump a “full and speedy recovery’ from COVID-19, after they were diagnosed with the virus earlier this week, but immediately went on the attack.

"I tell you, we all wish the President and the First Lady a full and speedy recovery. Sanders said at a rally for Democratic presidential nominee Joe Biden in Lebanon, N.H. “But I think what it does obviously is focus more attention on the COVID-19 pandemic," Sanders then said to a local media outlet right after.

TRUMP'S MEDICAL TEAM SAYS HE IS DOING 'VERY WELL'; OFFICIAL WARNS THAT NEXT 48 HOURS ARE 'CRITICAL' 

Sanders, who was a candidate in the Democratic presidential primary but has since endorsed Biden, spoke after Trump’s medical team said the President was doing “very well” and Mrs. Trump is doing “great.”

The Vermont senator jumped on the stark differences between Biden's and Trump's campaigning styles -- something that Trump mocked the former Vice President for in last week's debate, alleging that Biden couldn't fill an event with supporters "because nobody will show up."

Biden has held small, socially distanced events, which were exclusively virtual for months, while Trump has held rallies with thousands of people ignoring social distancing guidlines and largely rejecting face masks.

"Maybe some Republicans will make fun of us for this event. We limited attendance. We, as you can see spaced out. No one was let in without wearing a mask," Sanders said, referring to Saturday's event. "That's what we believe. And I think we're right on that."

"The President and the Republican Party...have downplayed this virus," Sanders said, adding that Trump has gone to "war against scientists."

Sanders addressed on one of Trump's favorite topics -- the state of the economy -- and claimed that the economy cannot be fixed until the pandemic is properly addressed.

"I think the people are concerned about getting a handle on this pandemic and understand they’re not gonna have the economy we need unless we get ahead of the pandemic," Sanders said.

"I think this crisis and the president’s illness makes it more apparent we need Biden in the White House," he added.

Trump was transferred to Walter Reed National Military Medical Center on Friday in what was described by doctors as a precautionary step after he tested positive for the virus late Thursday.

Doctors said on Saturday they were happy with Trump’s progress, that symptoms like a mild cough and fatigue had resolved, and that Trump was not having any difficulty walking or breathing.

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Trump, meanwhile, tweeted on Saturday afternoon that he was “feeling well” and thanked the staff at Walter Reed for their work.

However, a senior administration official told Fox News that there had been concern about the president’s condition on Friday and warned that “the next 48 hours will be critical.”

Fox News' Rob DiRienzo, Hillary Vaughn and John Roberts contributed to this report.