The US could soon become the epicenter of the coronavirus pandemic, the World Health Organization warned Tuesday.

A WHO spokeswoman, Margaret Harris, noted that there had been a "very large acceleration" in cases in the US in recent days.

In the past 24 hours, 85% of all new coronavirus cases were in the US and Europe. In the US, 553 people have died from COVID-19.

President Donald Trump has refused to impose a national lockdown, however, and has instead insisted the US will soon be "open for business."

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Though President Donald Trump insists the US should soon be "open for business," the World Health Organization has instead warned that the US could soon become the epicenter of the coronavirus pandemic.

A WHO spokeswoman, Margaret Harris, told a press conference in Geneva on Tuesday there had been a "very large acceleration" in US cases in recent days, according to Reuters.

Harris said that in the past 24 hours, 85% of all new reported coronavirus cases had been in the US and Europe, with 40% of those in the US.

Asked whether the US could become the "epicenter" of the crisis, she replied: "We are now seeing a very large acceleration in cases in the US. So it does have that potential."

She added: "We cannot say that is the case yet, but it does have that potential."

Her assessment came after Trump insisted the US should soon be "open for business."

"America will, again, and soon, be open for business — very soon," Trump told a White House coronavirus briefing on Monday.

The president is resisting calls to impose a national lockdown on the US, despite growing numbers of countries imposing strict restrictions on public movement.

UK Prime Minister Boris Johnson announced a national lockdown on Monday evening, with members of the public restricted from leaving their homes for nonessential reasons.