By Ted Hesson

WASHINGTON (Reuters) -A U.S. judge ordered Texas to move floating buoys that were placed in the middle of the Rio Grande to block migrants from illegally crossing the U.S.-Mexico border, a tentative win for President Joe Biden, whose administration sued the state.

U.S. District Court Judge David Ezra issued a preliminary injunction in Austin that requires Texas to relocate the buoys, currently near the city of Eagle Pass, to an embankment on the Texas side of the river. The Biden administration argued in a legal challenge that the barrier illegally disrupts navigation and was installed without permission from the U.S. Army Corps of Engineers.

The ruling is a setback for Texas Governor Greg Abbott, a Republican who contends that Biden, a Democrat, has been too lenient with border security as record numbers of migrants have been caught crossing illegally in recent years.

The floating barrier is one of multiple strategies Abbott has launched to deter migrants, including coils of razor wire placed along the riverbank.

"Governor Abbott announced that he was not 'asking for permission' for Operation Lone Star, the anti-immigration program under which Texas constructed the floating barrier," Ezra wrote in a 42-page order. "Unfortunately for Texas, permission is exactly what federal law requires before installing obstructions in the nation’s navigable waters."

Texas could appeal to the conservative-leaning 5th U.S. Circuit Court of Appeals.

(Reporting by Ted Hesson in Washington; editing by Mica Rosenberg, Jonathan Oatis and Bill Berkrot)