President Joe Biden is set to reinstate Covid-19 travel restrictions on non-US travellers from Brazil, Ireland, the UK and 26 other European countries that allow travel across open borders.
White House officials said that South Africa would also be added to the restricted list on Monday because of concerns about a variant of the virus that has spread beyond that nation.
Mr Biden is reversing an order from Donald Trump in his final days in office that called for the relaxation of the travel restrictions as of Tuesday.
The South Africa variant has not been discovered in the United States but another variant — originating in the UK — has been detected in several states.
Last week, Mr Biden issued an executive order directing federal agencies to require international air passengers to quarantine upon arrival in the US.
The order also requires that all US-bound passengers aged 2 and above get negative Covid-19 test results within three days before travelling.