The White House said Monday that the Biden administration will not yet lift a ban on international travelers from Europe and other regions, citing the ongoing threat of the delta variant of COVID-19 and a surge in cases nationwide.

Press secretary Jen Psaki said the president would continue the ban which was first announced by the Trump administration in January 2020 for some travelers from China before it was extended to Europe that March for the foreseeable future, adding that there was no timeline for it to end. Other countries have been added to the ban amid the spread of the coronavirus and its various strains.

The more transmissible delta variant is spreading both here and around the world, Psaki said during a press briefing. Driven by the delta variant, cases are rising here at home, particularly among those who are unvaccinated, and appear likely to continue in the weeks ahead.

Psaki noted that an ongoing vaccination campaign with high rates of inoculations was the main way those travel boundaries could eventually be lifted.

I dont have a timeline to predict for you because its all about what success we have at getting more people vaccinated, getting more vaccines out to the world and fighting the virus, she said.

The New York Times notes that the announcement will likely be a blow to the recovering travel industry, which had largely languished during the pandemic. Domestic flights have begun to surge again, and airlines had been hopeful for a near-full return to international routes as European nations began allowing fully vaccinated U.S. tourists again.

Biden had signaled earlier this month that he was considering how it could reopen the gate to European travel , but the latest shift reflects the ongoing struggle to rein in the delta variant.

The delta strain of the coronavirus continues to threaten hopes for an end to the pandemic, particularly as it spreads in parts of the U.S. with lower vaccination rates. The Centers for Disease Control and Prevention said last week that the delta variant is responsible for 83% of new cases of COVID-19 in the U.S., and the CDC director said it is one of the most infectious respiratory viruses scientists know of.

Vaccinations remain the best defense against severe illness and death from the coronavirus, and studies show those vaccines approved in the U.S. remain effective against the delta variant. About 97% of Americans now hospitalized for COVID-19 have not been vaccinated, a bleak figure that has troubled public health officials who have described this phase as a pandemic of the unvaccinated.