A senior Republican senator has told Donald Trump to “let the professionals do the talking” after the president repeatedly contradicted medical experts in recent weeks.

Mr Trump has sought to downplay the threat posed by coronavirus in the US, even as public health officials have warned of the potential for a serious outbreak.

The president has said a vaccine for the virus could be available “relatively soon”, despite experts saying it will take at least a year to produce one, and last week suggested virus cases were “going very substantially down, not up” as officials recorded numbers increasing.

Republican senator Lamar Alexander, the chairman of the Senate health committee, has intervened to assert that nonpolitical public health officials should be leading the response to the virus.

“My advice to the president and the vice president is let the professionals do the talking,” Mr Alexander said.

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Meanwhile, Democrats in Congress have said Mr Trump’s comments are undermining the work of his administration’s medical experts.

“It is pretty extraordinary that we have to have our medicine and health professionals counter-messaging the president ... that they have to correct the record,” Chris Murphy, a Democratic senator for Connecticut, told a hearing on Tuesday.

Earlier this week, Democrat Chuck Schumer, the Senate majority leader, accused Mr Trump of “downplaying” the threat posed by the outbreak.

“Even now, President Trump seems to be spending more of his time blaming the media, and blaming the Democrats, than being constructive. In fact, he blames everyone not named Donald Trump,” Mr Schumer said.

“We know the history of how these viruses spread and work. When you deny them, when you don’t let people know what’s happening and what to do about it, things get worse.”

Mr Trump casually described coronavirus as an issue that has “got the world aflutter” but insisted “it’ll work out” at a meeting of the National Association of Counties on Tuesday.

However, the president’s optimism has not been backed up by his experts, such as Dr Anthony Fauci, the director of the National Institute of Allergy and Infectious Diseases.

At a Senate hearing on Tuesday, Dr Fauci made it clear that neither coronavirus treatment nor a vaccine would be ready quickly, with potential treatment likely to come before a vaccine.

He said the pharmaceutical company Gilead was testing a potential treatment but officials would only know “in a few months” if it was effective.

Dr Fauci added data from China showed 80 per cent of people who get infected “do really quite well” and recover without any medical treatment, while 10 to 15 per cent get seriously ill, particularly those in high-risk groups such as the elderly or patients with other medical problems.

He also reiterated a vaccine would take at least a year to a year and a half to be produced.

Mr Alexander has argued it is better for senators to hear updates on the virus from public health officials to avoid partisan politics coming into play.

“The more we listen to the heads of those agencies, I think the better. Because if the administration talks too much people think that it’s taking credit,” the Republican senator said.

“But if the Democrats talk too much they’ll think they’re playing politics.”

US health officials have confirmed nine deaths from coronavirus, all in Washington state, and more than 100 cases across the country, as of Wednesday morning.