Donald Trump ripped Senator Elizabeth Warren after the progressive Massachusetts Democrat dropped out the presidential primary, contending she stayed in long enough to block Senator Bernie Sanders from winning the party's nomination.

Ms Warren and Mr Sanders, a self-described "democratic-socialist, were vying for the same lane in the Democratic nominating contest - and the same voting bloc. He won the struggle, becoming the party's frontrunner to take on Mr Trump until former Vice President Joe Biden's sizeable win in South Carolina prompted the other top moderates to drop out and endorse him, fueling his Super Tuesday romp that has Mr Sanders suddenly running second.

Had Ms Warren also dropped out after her big loss Saturday in the Palmetto State, political experts say most of her voters would have shifted to Mr Sanders, creating at least a much tighter race between he and Mr Biden.

The president for years has publicly feuded with the Oklahoma-born law school professor and bankruptcy law guru, pouncing on her claims to have Native American ancestry, which proved to be false and prompted an apology. He appeared to revel Thursday morning in her exit from the race.

"Elizabeth 'Pocahontas' Warren, who was going nowhere except into Mini Mike's head, just dropped out of the Democrat Primary...THREE DAYS TOO LATE," Mr Trump tweeted from the White House residence minutes after her announcement. (There was no US Marine outside the West Wing at that time, a sign the president is not in the West Wing.)

The president has not hidden his desire to face Mr Sanders in the general election, something aides privately confirm.

"She cost Crazy Bernie, at least, Massachusetts, Minnesota and Texas. Probably cost him the nomination!" he wrote, before adding this dig: "Came in third in Mass." That was a reference to her loss Tuesday in her adopted home state.

Meantime, the president also raised eyebrows with an earlier tweet that claimed "I NEVER said people that are feeling sick should go to work."

Yet, during a Wednesday night call-in interview with Fox News Channel's Sean Hannity, the president said the opposite.

"Well, I think the 3.4 percent is really a false number," Mr Trump said, referring to the World Health Organization's current coronavirus mortality rate. "Now, and this is just my hunch ... but based on a lot of conversations with a lot of people that do this. Because a lot people will have this and it's very mild. They'll get better very rapidly. They don't even see a doctor. They don't even call a doctor."

"You never hear about those people. So you can't put them down in the category of the overall population in terms of this corona flu ... or virus. So you just can't do that," he added. "So if, you know, we have thousands or hundreds of thousands of people that get better, just by, you know, sitting around and even going to work -- some of them go to work, but they get better."

But hours earlier, US Centers for Disease Control and Prevention Director Robert Redfield said the opposite from the White House briefing room.

"I think the most important thing, for many of those individuals that might be a little type A: If you get sick, stay home," he told reporters. "You're not helping your colleagues by going to work sick."