The White House on Thursday said there is no timetable for lifting travel restrictions on southern African countries, even as a new case of the omicron variant was identified in the U.S.

Press secretary Jen Psaki defended the ban to reporters, saying President Biden was following the advice of public health experts who were concerned about large numbers of cases stemming from an unknown variant.

"I wouldn't anticipate the lifting of restrictions before we know more about the variant," she said. "None of these are meant to be permanent, none of them are meant to be a punishment, they're all put in place to protect the American people to hopefully save more lives." 

There have been two cases of the omicron variant identified in the U.S. over the past two days. The first was found in San Francisco, the patient had returned from South Africa four days before that country announced the discovery of the omicron variant.

The second was identified in someone from Minnesota, whose only recent travel had been to New York. He developed symptoms on Nov. 22, a full week before the travel ban took effect, an indicator that the strain was already circulating in the U.S.

The White House on Monday implemented a ban on incoming travelers from South Africa, Botswana, Zimbabwe, Namibia, Lesotho, Eswatini, Mozambique and Malawi due to concerns about the omicron variant. 

But even at that point, the variant had been found in more than a dozen countries, including some in Europe, which were not affected by the ban. The ban also doesn't apply to U.S. citizens or permanent residents, only foreign nationals.

The decision sparked immediate backlash from the international community and public health experts, who say it is ineffective and punitive against African countries, especially as Western countries have failed to deliver needed vaccine supplies and logistics to the continent.

United Nations Secretary-General António Guterres described the response as “travel apartheid.”

Anthony Fauci, the White House chief medical adviser, said Wednesday he "felt really badly" about the restrictions, but maintained they are necessary to buy time to better understand the variant, not to keep it out of the U.S. completely.