Biden says US Covid-19 response 'shouldn't' be political issue

US President Joe Biden said Thursday the United States' Covid-19 response shouldn't be politically divisive and that he hoped for bipartisan backing for his plan to tackle the pandemic over winter.

"It's a plan that I think should unite us," he said, speaking from the headquarters of the National Institutes of Health in a Washington suburb.

"I know Covid-19 has been very divisive. In this country, it's become a political issue... A sad, sad commentary. It shouldn't be, but it has been."

Biden's remarks come as the Omicron variant, first reported in South Africa last week, continued to spread globally.

Two cases have so far been announced in the United States - the second involving a Minnesota man with no recent international travel history, signalling the strain is already circulating inside the country.

The man, who was also fully vaccinated and received a booster shot, experienced mild symptoms that have since cleared, local health authorities said.

Biden's winter plan includes ramping up booster shots for all adults, vaccinating children, expanding at-home free testing and stronger travel protocols.

The travel measures will include requiring anyone arriving in the United States to take a test within one day of their flight.