The UK's original plan to deal with the coronavirus by achieving "herd immunity" within the population, would have been "catastrophic" and caused "a lot of death," President Donald Trump has said.

The UK reportedly abandoned its original plan for the UK population to achieve 'herd immunity' after experts warned it would result in up to 250,000 deaths.

Trump said a similar strategy in the US would result in millions dying across the country.

Boris Johnson's government is under growing pressure domestically to defend its lack of preparation for the current crisis.

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Donald Trump has said that Boris Johnson's abandoned plan for creating "herd immunity" to the coronavirus in the UK would have been "catastrophic" and caused "a lot of death."

The president said that the UK government's original coronavirus strategy plan, which involved allowing the virus to spread in order to achieve resistance to the virus in the population, would have caused millions of deaths if adopted in the US.

"If you remember, they were looking at that concept - I guess it's a concept if you don't mind death, a lot of death - but they were looking at that in the UK, remember," Trump told a White House press briefing on Tuesday.

"And all of a sudden they went hard the other way because they started seeing things that weren't good, so they put themselves in a little bit of a problem."

He added: "It would have been very catastrophic I think if that would have happened."

Watch Trump label original UK coronavirus plan 'catastrophic'

At the same briefing, Dr Deborah Birx, the White House's coronavirus response coordinator, said the UK had a dangerously low number of ventilators, which are respiratory machines being used to treat patients suffering from the worst effects of the virus.

"We are worried about groups all around the globe," she said.

"I don't know if you heard the report this morning, there are 8,000 ventilators in the UK.

"If you translate that to United States, that would be like the United States having less than 40,000 ventilators. We have five times that."

Trump last week claimed that Boris Johnson pleaded with the president for the US to send ventilators to the UK.

"Before he even said hello, he said, 'We need ventilators,'" Trump told reporters.

The president's comments are politically embarrassing for Johnson, who is currently struggling to answer questions about why it is testing for the coronavirus at a significantly lower level than other developed nations.

Boris Johnson initially resisted calls to close schools or mass gatherings even as deaths in other European countries including Italy surged.

The comparatively relaxed measures reflected the fact Downing Street was pursuing a strategy of "herd immunity," according to multiple reports, a concept which the UK's chief science advisor openly discussed in a television interview.

However, scientists advising the government subsequently warned that the UK's strategy could result in up to 250,000 deaths, which persuaded the UK to change course abruptly and announce strict lockdown measures in line with most other European countries.

Johnson's government is under growing pressure to explain its slow response to the outbreak and its lack of testing and vital medical equipment.