US President Donald Trump has tested negative for the new coronavirus, his physician said, following concerns over his exposure to COVID-19.

Trump agreed to the test after coming into contact with several members of a Brazilian presidential delegation visiting his Florida resort who have since tested positive.

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Prior to his testing on Friday, the Republican president said his personal physician told him he did not show symptoms and did not need to take the test. But the 73-year-old president decided to do it anyway after repeated questions from reporters about why he was hesitating to undergo screening when he had been exposed to at least three people who have tested positive.

"This evening I received confirmation that the test is negative," the president's physician Sean Conley said in a memo on Saturday.

COVID-19, the disease caused by the new coronavirus, has killed at least 51 people in the US and upended daily life across the country, with millions working from home and schools shut.

New York, the most populous US city, saw its first coronavirus death on Saturday, as store shelves were stripped bare after days of panic buying.

Across the Hudson River in Teaneck, New Jersey, Mayor Mohammed Hameeduddin called for a citywide self-quarantine after 18 cases were confirmed in the township.

"What we are saying is that we are ground zero," Hameeduddin said. "Expect or act as though you're going to infect somebody or somebody is going to infect you."

The pandemic has now infected more than 2,200 people in the US. Globally, it has killed more than 5,800 people in at least 137 countries.

Ban extended to UK and Ireland

Meanwhile, Vice President Mike Pence announced further curbs on travel to the US, saying a ban imposed on European nations over the pandemic would be extended to the UK and Ireland on Tuesday.

The restrictions threw airports across the country into disarray, with incoming travellers forced to wait hours for medical screenings before passing through customs.

Acting Homeland Security secretary Chad Wolf said his office was working with airlines to improve screening times.

Trump advised against non-essential travel and said officials were also considering imposing domestic restrictions.

"If you don't have to travel, I wouldn't do it," Trump said at a White House news conference. "We want this thing to end."

In an official proclamation, he also named Sunday a national day of prayer "for all people who have been affected by the coronavirus pandemic".

Trump declared a national emergency on Friday, freeing up some $50bn in disaster relief funds.

The US House of Representatives also passed a bill - crafted by Democrats in consultation with the Trump administration - to provide billions of dollars for free virus testing, emergency paid sick leave and family leave.

It is expected to pass the Republican-majority Senate.