Donald Trump made clear Friday that America's lockdown due to the coronavirus outbreak will go on for longer than some may expect.

"We're not going anywhere. We're going to be here," the president said while applauding Americans for purchasing fewer groceries and supplies than they typically do, allowing others to get what they need as they hunker down at home.

That comment came as Mr Trump and his secretary of Health and Human Services, Alex Azar, described illegal migrants coming over the US-Mexico border as threats to further infect the American general population. They also contended migrants could give the virus to American borer patrol personnel, though they offered no data linking migrants from Central and South America to the virus outbreak inside the United States.

Mr Trump ran on a hardline immigration platform in 2016, and has implemented many such policies as president. Aides have signalled he will again use the issue in his re-election campaign, and his early 2020 campaign rallies supported those predictions.

Minutes after New York Governor Andrew Cuomo announced all non-essential workers in New York City should remain at home until further notice, Mr Trump told reporters he does not foresee ever giving such a national shelter-in-place – a term the New York chief executive avoids – order.

"I don't think we'll ever find that necessary," he said, giving state and local officials in places like San Francisco, New York City and Miami high marks for their moves to limit the amount of people milling about in public.

COVID-19 is highly contagious, with some experts and lawmakers saying it is as easily spread as the deadly 1918 influenza strain that killed millions around the world.

Meantime, a day after he was criticised for giving false hope to Americans by saying a common Malaria drug could be used to treat coronavirus, he lashed out at a NBC reporter who asked if he has given Americans false hope. When Peter Alexander asked what the president would say to Americans who are scared, Mr Trump shook his head and attacked the television reporter.

"I say you're a terrible reporter," Mr Trump said, saying Mr Alexander should "get back to reporting" and cease the "sensationalism."