Pence defends Europe travel curbs as more US coronavirus cases expected

US Vice President Mike Pence on Thursday defended the Trump administration's new restrictions on travel from European nations, saying the epicentre of the coronavirus has shifted from Asia to Europe.

In a round of television interviews, the Republican vice president said thousands more COVID-19 cases were expected in the United States, and that clamping down on European travellers was just part of the administration's strategy as US cases swell.

The European Union on Thursday criticized the US travel curbs, saying it was not consulted first before US President Donald Trump announced them in a Wednesday night address to the nation.

Pence also said officials are seeking to ramp up testing in all 50 US states and pointed to efforts by commercial laboratories including Laboratory Corporation of America Holdings (LabCorp) and Quest Diagnostics Inc, but gave no other details.

Health experts have said a shortage of diagnostic test kits has made it difficult to gauge the full scale of outbreaks in the United States and curtail transmission of the virus.

The hardest-hit US states, such as New York and Washington state, have struggled to quickly expand testing capacity to make such screening widely available.