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By Bernd Debusmann Jr
BBC News, Washington
The Biden administration has sued Texas over a floating barrier installed by the state in the Rio Grande river to deter migrants on the US-Mexico border.
The barrier, made partly of orange buoys attached by webbings, was announced by state's Republican governor Greg Abbott in early June.
Federal authorities say the barriers in the river flout federal law and present "humanitarian concerns".
Ahead of the lawsuit, Mr Abbott vowed to "see" the government in court.
First announced in June, the barriers cover about 305 metres (1,000ft) of the Rio Grande. The buoys are connected with webbing and anchored to the bottom of the river.
State officials have argued it will help secure the border. Immigrant advocates have said it may be ineffective and potentially dangerous to migrants.
The barriers are already the subject of another lawsuit from a local kayak company.
In a nine-page lawsuit filed to a federal court in Austin, the Justice Department argued that state officials were required to seek federal permission to put the barriers in place.
By not doing so, federal officials argue, Texas violated federal laws governing navigable waterways.
"We allege that Texas has flouted federal law by installing a barrier in the Rio Grande without obtaining the required federal authorization," associate attorney general Vanita Gupta said in a statement.
"This floating barrier poses threats to navigation and public safety and presents humanitarian concerns," the statement added. "Additionally, the presence of the floating barrier has prompted diplomatic protests by Mexico and risks damaging US foreign policy."
The Biden administration had previously warned Texas authorities that they could avoid a legal battle by removing the obstacles from the river.
On Monday, Mr Abbott struck a defiant tone and blamed President Joe Biden for a "record-breaking level of illegal immigration" that made the barrier necessary.
"Texas will see you in court, Mr President," Abbott said in a statement.
State officials have repeatedly defended the barriers as part of a wider effort - known as Operation Lone Star - that has seen Texas authorities take increasingly aggressive steps to secure the state's border with Mexico.
Since the operation was first launched in March 2021, Texas claims that over 394,200 illegal immigrants have been apprehended and 31,300 criminal arrests made.
Operation Lone Star has come under renewed public scrutiny following a report in the Houston Chronicle that officers assigned to the initiative expressed concern over "inhumane" behaviour towards migrants in the Eagle Pass area, including withholding water despite intense heat and pushing migrants back into the river towards Mexico.
Immigration advocates have said that the floating barriers near Eagle Pass are unlikely to have a substantial impact on the flow of migrants crossing the border and may actually make the crossing more dangerous.
The barriers are the subject of a separate lawsuit filed on behalf of a local kayak tour operator who has argued that the buoys damage his business and destroy local flora and fauna.