In his latest rambling and at times bad-tempered press conference, Donald Trump made a series of false and misleading claims about the escalating coronavirus pandemic that is killings hundreds of Americans a day.

In what has become a daily opportunity for Mr Trump to attack his political adversaries, the US president used Sunday's briefing to lash out at a Democratic governor, brand a reporter a “wise guy”, and advise engineers on how to repair highways.

“There is a governor, I hear him complaining all the time. Pritzker, I hear him, he’s always complaining,” Mr Trump said of Illinois governor Jay Pritzker, adding: “He has not performed well.”

It came hours after Mr Pritzker, whose state has been hit hard by the virus, criticised the president's calls for local governments, rather than the White House, to take the lead on stockpiling for potential disasters.

Announcing his administration had stockpiled 29 million doses of hydroxychloroquine, Mr Trump said: “I think, as you know it’s a great malaria drug, it’s worked unbelievably, it’s a powerful drug, on malaria, and there are signs it works on this, some very strong signs.”

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Conceding it was only “being tested now” for its effectiveness against Covid-19, Mr Trump went on to say: “I just think it’s something, you know the expression, ‘I’ve used it, what have you got to lose?'”

He added: “I’ve seen things that I sort of like, so what do I know I’m not a doctor, I’m not a doctor but I have common sense.”

Dr Anthony Fauci, the government’s leading infectious disease expert, had earlier said there was little evidence so far that the anti-malarial drug was effective against the virus.

“In terms of science, I don’t think we can definitively say it works,” he told CBS’s Face the Nation. “The data are really just at best suggestive. There have been cases that show there may be an effect and there are others to show there’s no effect.”

When Dr Fauci, who was in attendance at the White House briefing, was later asked by a reporter about the drug’s effectiveness, Mr Trump blocked him from answering.

“You know how many times he’s answered that question – 15 times,” said Mr Trump. “You don’t have to ask that question.”

When a CNN reporter asked why he was “promoting” the drug and not leaving it to health experts, Mr Trump admitted it “may not work”, before saying: “Only CNN would ask that question. Fake news … bunch of fakers.”

Asked about the potential to escalate road repairs amid a sharp drop in highway usage, Mr Trump hit out at US engineers for what he perceives to be overly expensive and ineffective fixes.

“They don’t do construction techniques that work and that are better. I see a highway, which is what I do, I do construction, what I did. I see a highway that’s good, but it’s got a bad top, and it’s got a big base, a concrete base underneath,” Mr Trump said.

“And I’ll see them come in … and they rip the hell out of it, they take out the base, they take out everything, now they pour a new base that isn’t as good, isn’t as deep, isn’t as thick.”

Mr Trump provided no evidence for his claims, but went on to complain repairs took “forever” and that many would “crack” after completion.

“They spend 10, 15, 20 times more money than they have to … they take the most expensive solution and the bottom line, the job itself is far worse,” he added.

Mr Trump next falsely claimed the US had undergone “the greatest economic boom in history” under his administration, before attacking an Associated Press reporter who asked about the adequacy of the government’s preparedness for a pandemic.