Donald Trump has directly urged Americans worried about Covid-19 to take a little-studied anti-malaria drug for the disease, despite potentially serious side effects and a lack of data on safety and efficacy in treatment of the pandemic virus.

At a lengthy, rambling and combative briefing on Saturday afternoon, the president also sought to discredit media reports of his administration’s failures and called some outlets in the White House press corps “fake news”.

Media reports about shortages of ventilators and personal protective equipment, he claimed, relied on state governors asking for more supplies than they needed.

According to researchers at Johns Hopkins University in Maryland, by Saturday evening more than 305,000 cases of Covid-19 had been confirmed in the US, resulting in more than 8,000 deaths. New York is by far the state worst hit.

Scientists around the world are looking for potential treatments but so far have not found a success. The drug repeatedly pushed by Trump, hydroxychloroquine, has only shown anecdotal promise.

The drug is used to treat malaria, arthritis and lupus. Reports of its potential have driven up sales and made it difficult for Americans who rely on the drug to fill prescriptions.

“What do you have to lose? What do you have to lose?” Trump said from the White House podium. “Take it.”

He also said he “may take it” himself, though he would “have to ask my doctors about that”.

The president’s own public health advisers, who stood with him in the briefing room on Saturday, have warned against taking hydroxychloroquine for Covid-19.

On 24 March, for example, Dr Anthony Fauci, the National Institute of Allergy and Infectious Disease director, answered a reporter’s question about whether the drug was considered a treatment for Covid-19.

“The answer is no,” Fauci said, “and the evidence that you’re talking about … is anecdotal evidence.”

On Saturday the Food and Drug Administration commissioner, Dr Steven Hahn, said physicians could prescribe hydroxychloroquine under emergency use authorization.

“We don’t want to provide false hope but we definitely want to provide hope,” he said.

Trump’s urging came moments after another senior health adviser, Dr Deborah Birx, told Americans the coming weeks would be “the moment to do everything you can to keep your families and friends safe” by following federal physical distancing guidelines.

The White House’s own projections show 100,000 Americans could be killed by the virus. On Saturday, Trump said: “There will be a lot of death”.

“It’s therefore critical certain media outlets stop spreading false information,” he said. “I could name them, but it’s the same ones, always the same ones.”

Earlier, the New York governor, Andrew Cuomo, announced his state had looked to China for ventilator supplies.

“We’re not yet at the apex,” said Cuomo, who described the crescendo of cases to come as “the number one point of engagement of the enemy”.

Cuomo said he had obtained 1,000 ventilators from the Chinese government with the help of billionaires Joseph and Clara Tsai and the Alibaba founder Jack Ma. Oregon had loaned New York another 140, he said.

Doctors test hospital staff for coronavirus outside the St Barnabas hospital in New York. White House projections show 100,000 Americans could be killed by the virus. Photograph: Misha Friedman/Getty Images

The Trump administration has sought to redefine the national strategic stockpile as a “back up” for states, and avoid coordinating a response to the pandemic. On Saturday, Trump tried to claim credit for the 1,000 ventilators sent to New York by China and said, “two very good friends of mine brought him those ventilators”.

In his morning press conference, Cuomo said New York had 113,704 confirmed cases of Covid-19 and a death toll of 3,565. Most deaths were in New York City, with nearly 1,000 in other parts of the state.

Current projections put the peak of the pandemic in New York between four and 14 days away. Officials hope physical distancing will slow the spread of the disease and forestall the possibility of running out of ventilators and hospital beds.

Cuomo admitted he hoped to see the apex soon, so the experience would soon end. The pandemic, “stresses this country, this state, in a way nothing else has frankly in my lifetime”, he said.

Cuomo’s briefing from the New York state capital, Albany, offered another contrast in leadership with the president in Washington. While Cuomo’s briefings convey alarming statistics, his frank descriptions of shortages and personal struggles have been praised.

On Saturday, Cuomo said the state had a signed contract for 17,000 ventilators, a deal he was later told could not be done because many had already been bought by China.

As Cuomo spoke, Trump retweeted articles about hydroxychloroquine, from rightwing sources.

The US federal government’s response to the outbreak has been defined by bungled testing, poor coordination, low stockpiles and planning failures. Federal failure to intervene in supply chains has led to bidding wars for masks and other personal protective equipment, governors have said.

The White House has repeatedly claimed it has 10,000 ventilators in the national stockpile. However, states have reported some of those ventilators are unusable, after the administration failed to ensure the stockpile was properly maintained.

Trump has repeatedly caused confusion, often during hours-long press conferences. On Saturday, he also attacked his probable challenger in November, Joe Biden, and the intelligence official he fired on Friday night; insisted the US economy would soon have to “reopen” despite expert predictions of a lengthy shutdown to deal with the virus; and defended Republican governors who have not ordered social distancing measures.

Such states, he said, had “big land, few people and they’re in very good shape”.