WASHINGTON - The Trump administration on Wednesday unveiled new rules that would allow officials to detain migrant families indefinitely while judges consider whether to grant them asylum in the United States.

The rules, which are certain to draw a legal challenge, would replace a 1997 legal agreement that limits the amount of time US immigration authorities can detain migrant children. That agreement is generally interpreted as meaning families must be released within 20 days.

Administration officials blame the so-called Flores Settlement Agreement for a spike in immigration, especially of Central American families, saying it encourages migrants to bring children with them so they can be released into the United States while their court cases are pending.

Families typically have to wait several months for their cases to work their way through immigration court, and the new rule would allow DHS to keep those families at detention facilities.

The settlement had placed limits on how long children could be held in detention, leading the administration to release tens of thousands of families pending the resolution of their cases.

Acting Secretary of Homeland Security Kevin McAleenan, announcing the new rule, said those releases were an incentive for immigrants to travel with children and that the government believes the new detention rule will have a deterrent effect.

McAleenan said the government believes some families apprehended on the border were "fraudulent" based on DNA testing of some migrants in pilot programs implemented in recent months.

"No child should be a pawn," McAleenan said at a news conference announcing the rule. "Or as one gentleman in Guatemala told me, 'as a passport to the United States.'"

The rule will be published in the Federal Register on Friday and will take effect 60 days from that publication. The implementation deadline could slip, however, depending on the success of the likely court challenges.