The US government is suing Arizona’s governor over the construction of a makeshift barrier made of shipping containers at the US-Mexico border.
Governor Doug Ducey began building the barrier earlier this year, saying it was an attempt to “secure” the border.
But in its lawsuit, the government claimed Arizona was trespassing on federal lands.
Hundreds of thousands of people have been detained while attempting to cross the border in recent months.
President Joe Biden has been criticised by opponents – including Republican Governor Ducey – over his administration’s handling of border issues.
The legal action comes three weeks before Governor Ducey’s last day in office, when he will step aside for Democrat Katie Hobbs who has previously said she opposes the barrier.
Ms Hobbs is yet to decide on what to do with the containers. She has said that she is exploring all options, and warned that removing the containers may be costly.
The government is seeking a court order to stop the building of the barrier and to remove the shipping containers in Arizona’s San Rafael Valley.
It cites environmental concerns associated with the construction, claiming Arizona has “cut down and removed scores of trees, clogged drainages, and degraded the habitat of species listed under the Endangered Species Act”.
The federal government is also seeking compensation to fix any damage caused by the barrier.
Governor Ducey has previously said that his state would remove the shipping containers, which he described as a temporary barrier, but he has asked the Biden administration for a timeline on when it will fill remaining gaps in the permanent border wall.
In August, he signed an executive order that directed his state to immediately fill the gaps after he had criticised the federal government for not doing enough to address a record-breaking number of migrants arriving at the US-Mexico border.
Arizona’s move has also been met with resistance from environmental activists, who have escalated protests around construction sites in recent days and slowed down progress.