President Joe Biden will impose a ban on most non-US citizens entering the country who have recently been in South Africa starting Saturday in a bid to contain the spread of a new variant of Covid-19, a senior US public health official said.

Biden on Monday is also reimposing an entry ban on nearly all non-US travellers who have been in Brazil, the United Kingdom, Ireland and 26 countries in Europe that allow travel across open borders.

"We are adding South Africa to the restricted list because of the concerning variant present that has already spread beyond South Africa," said Dr Anne Schuchat, the CDC's principal deputy director, in an interview on Sunday.

She added the agency was "putting in place this suite of measures to protect Americans and also to reduce the risk...