Texas Gov. Greg Abbott expressed alarm Sunday about a surge in crossings at the U.S.-Mexico border if a key immigration policy, Title 42, is allowed to expire this week and called on courts to step in.

Abbott said that public health concerns should prompt courts to intervene and prevent the policy from expiring. Former President Donald Trump implemented Title 42 in early 2020 amid the COVID-19 pandemic.

Last week, the D.C. Circuit Court of Appeals ruled that Title 42 is still set to expire on Wednesday, Dec. 21. Abbott and other Republicans said that illegal border crossings are expected to increase after that.

A coalition of 19 Republican-leaning states was pushing to keep the asylum restrictions. Under the rule, illegal immigrants have been denied the ability to seek asylum under U.S. and international law 2.5 million times since March 2020 on grounds of preventing the spread of COVID-19.

Immigration advocates had argued that the United States was abandoning its longstanding history and commitments to offer refuge to people around the world fleeing persecution, and sued to end the use of Title 42. They’ve also argued the restrictions are now outdated due to natural immunity and vaccines.

“But some do come across with COVID, and no one knows exactly who comes across with COVID,” Abbott said Sunday. “These people are not tested when they come across the border. Who knows how many people have COVID ... the answer is nobody knows because nobody is testing.”

Previously, Abbott ended all state COVID-19 restrictions in 2021 and banned all COVID-19 vaccine mandates.

Border cities, most notably El Paso, Texas, are facing a daily migrant influx that the Biden administration expects to grow if asylum restrictions are lifted. Tijuana, the largest Mexican border city, has an estimated 5,000 people in more than 30 shelters, Enrique Lucero, the city’s director of migrant affairs said this week.

Some Democrats, however, argue that Title 42 isn’t an immigration policy and should be rescinded.

“Title 42 was put in place at the beginning of the COVID-19 pandemic as health policy,” Sen. Alex Padilla (D-Calif.) told ABC News on Sunday. “Even then I disagreed, but that’s what brought Title 42 to bear. We’re in a much different place when it comes to COVID today.”

Meanwhile, Sen. Sherrod Brown (D-Ohio) told NBC News on Sunday that Democrats and Republicans who respectively control the Senate and House should work in a bipartisan manner on immigration reform.

“Maybe with this new Republican House and Democratic Senate, we finally get serious about immigration reform and quit demagoguing this issue by pointing fingers and say that the disaster is about to happen,” Brown said. “I think that the administration will figure this out, short-term, but it’s clear we’ve got to get serious as a body, and it’s going to take both parties. Instead of trying to gain on bashing immigrants or gain on appealing to new citizens, we’ve got to get serious about that.”

In a related development, a federal judge in Amarillo, Texas, ruled Thursday that the Biden administration wrongly ended a Trump-era policy to make asylum-seekers wait in Mexico for hearings in U.S. immigration court. The ruling had no immediate impact but could prove a longer-term setback for the White House.