PENSACOLA, Florida: Agreeing with the state's Republican attorney-general, a federal judge in Florida has ruled that the White House policy of releasing people who illegally cross into the US from the Mexican border, rather than detaining them, violates immigration law.

US District Judge T. Kent Wetherell in Pensacola blocked the Biden administration from continuing to implement a 2021 Department of Homeland Security (DHS) memo, which authorized "alternatives to detention" in overcrowded detention centers, such as ankle bracelets and phone monitoring.

The policy is known as "catch and release" by Republican critics.

Appointed by former Republican President Donald Trump, Wetherell said federal immigration authorities cannot carry out those alternatives under existing law, agreeing with the challenge by Florida Attorney-General Ashley Moody.

Referring to non-US citizens who cross the border illegally, Wetherell said, "Defendants have effectively turned the Southwest Border into a meaningless line in the sand and little more than a speed bump for aliens flooding into the country."

Wetherell gave the administration seven days to file an appeal.

In a statement, Moody said that Wetherell's decision "affirms what we have known all along, that President Biden is responsible for the border crisis and his unlawful immigration policies make this country less safe."

The ruling could lead to a significant increase in the number of migrants held in detention centers, as the Biden administration stressed it lacks the resources and detention capacity to process a recent surge of migrants.

Florida and 19 other Republican states are separately challenging another administration policy that would allow hundreds of thousands of migrants from Cuba, Haiti, Venezuela and Nicaragua to be released into the US annually, rather than being detained.