It targets the tens of thousands of Central American families who cross into the U.S. through Mexico. But it would also affect people from Africa, Asia and South America who also seek refuge at the southern border.
Immigrant advocates say the plan is illegal because it circumvents the process Congress has established for asylum.
Nearly two dozen immigrants have been allowed to cross the U.S.-Mexico border to seek asylum.
The immigrants were allowed in Tuesday, the same day the Trump administration planned to launch a drastic policy change designed to end asylum protections for most migrants who travel through another country to reach the United States.