The White House on Thursday said there is no timetable for lifting travel restrictions on southern African countries, even as two new cases of the omicron variant were 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.”

But the new cases demonstrate that there is at least some local transmission of the variant and that it had arrived in the U.S. before the Biden administration imposed travel restrictions on eight African countries, including Botswana and South Africa where early cases of the variant were detected.

The ban took effect on Monday. 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.