The Biden administration is set to tighten access to asylum at the U.S.-Mexico border via a new regulation that could be issued as soon as Thursday, four sources familiar with the matter said. The move is aimed at reducing illegal crossings.

The regulation would require migrants to be assessed at an initial asylum screening stage to see whether they should be barred from asylum and quickly deported, said the sources, who requested anonymity to discuss internal government planning. They added that the measure appeared limited in scope.

The migrants would be assessed related to criminality and security threats, two of the sources said.

The new regulation would improve efficiency by screening asylum-seekers earlier in the process to determine whether they should be barred, one of the sources, a U.S. official, told Reuters. It would be issued as a proposed regulation and finalized at a later date, the official said.

U.S. President Joe Biden, a Democrat seeking another four-year term in the November 5 election, has struggled with at times high numbers of migrants caught crossing the U.S.-Mexico border since taking office in 2021. Former U.S. President Donald Trump, Biden's Republican challenger, has criticized Biden for rolling back more restrictive Trump-era policies.

The Biden administration has considered a more sweeping move to block asylum-seekers and migrants at the border using a federal statute deployed by Trump in his travel bans, but is not immediately planning to take that step, the sources said.

Biden implemented new asylum restrictions last year, but their effectiveness has been limited by a lack of resources to process arriving migrants.

The regulation expected to be issued this week could mean potentially thousands of people would be more quickly deported from the U.S. per year, two of the sources said, a relatively small number compared with the total number caught crossing illegally.