The Trump administration is moving ahead with a plan to limit when and where foreign nationals can apply for asylum at the U.S. border with Mexico.

The administration will publish a new rule aimed at pushing asylum seekers to already crowded border crossings and deny the opportunity to apply for asylum to nearly all immigrants caught crossing the border illegally.

Critics said the rule oversteps the president’s legal authority to change immigration law and is certain to end up in court.

In a call with reporters Thursday, senior administration officials said President Trump is expected to sign a presidential proclamation that blocks illegal border crossers from the asylum process. The administration officials said the president has the authority to limit asylum for some foreigners under the Immigration and Nationality Act.

The rule change and expected proclamation—which could be signed as early as Friday and effectively changes U.S. immigration law—is aimed at reducing the volume of immigrants crossing the border illegally to seek asylum in the U.S. It comes as part of a focus by the president on a group of thousands of mostly Central American migrants making their way to the U.S. in multiple caravans traveling through Mexico.