President Donald Trump suspended travel from Europe to the United States for 30 days in a "tough" new effort to halt the spread of the novel coronavirus pandemic that has sparked a run on the stock market and is rapidly multiplying.

The ban will not include travellers from the United Kingdom, which recently left the European Union, Trump said.

In a primetime address from the Oval Office to a worried nation, Trump sought to rebuff critics who say his leadership has been lacking during the crisis, insisting that "the virus will not have a chance".

"This is the most aggressive and comprehensive effort to confront a foreign virus in modern history," he said.

He announced a series of measures designed to ease the financial burden for people having to take weeks off from work while on quarantine.

But his most far-reaching announcement was the halt on European travel.

Trump said this would go into effect from "midnight Friday".