WASHINGTON—The Trump administration has moved to deny bail to some asylum seekers at the southern border, amid a surge of Central American immigrant families.

If the ruling issued by Attorney General William Barr Tuesday takes effect, it could mean that asylum seekers could spend more time in jail while their cases are decided. The ruling is due to be implemented in 90 days so that the Department of Homeland Security can conduct additional operational planning, the Justice Department said.

But the ruling has limited practical implications because the administration is barred from holding families for more than 20 days under a court settlement and has opted to stop separating children and adults as a matter of practice.

The government has also said it no longer has space to detain most of the thousands of immigrants arriving each day at the U.S. border with Mexico. Even in cases when it does, the government says it is running out of money to drive them to jail.

The Trump administration has said that the arrivals of people seeking asylum, often in large groups and including children, have brought the system to a breaking point. An 855,000-case backlog in the immigration courts means families who file claims could wait months or years to have them heard. And Mr. Trump and key aides have criticized the practice—which the president has called catch-and-release—of letting people enter the U.S. and work while waiting for their asylum hearing.