Hundreds of National Guard troops from Texas have arrived at an army training centre outside Chicago to support US President Donald Trump's immigration crackdown.
Trump has branded Chicago a war zone, following recent protests against federal immigration officials in the third-largest US city.
The deployment comes amid opposition from local officials. Illinois Governor JB Pritzker has accused the Trump administration of an authoritarian march and said the state would use every lever at our disposal to stop this power grab.
Sources told CBS News, the BBC's US partner, that some troops could begin their assignments as early as Wednesday.
Trailers have been set up as temporary living quarters on the Army Reserve Training Center about 50 miles (80km) south-west of Chicago. Fencing was also put up around the training facility late on Tuesday.
Local officials have said they have received few details on the troop assignments. Trump argues the use of the troops is necessary to quell violence in Democratic-controlled cities, crack down on crime and support his deportation initiatives.
National Guard troops have limited power. They do not enforce the law, or make arrests, seizures, or searches - their role is instead about protecting federal officers and property.
Trump has already sent guard members into Los Angeles and Washington, DC, and has ordered them to enter Memphis and Portland. A federal judge temporarily barred troops from deploying to Portland; however, another judge has allowed the Chicago deployment for now.
Chicago has seen an increase in protests over immigration enforcement in the city, many of them happening outside US Immigration and Customs Enforcement (ICE) facilities. Last weekend, US Border Patrol personnel shot and injured a woman after cars were rammed into ICE vehicles, although local media report her lawyer has contested parts of the government's version of events.
A hearing is scheduled for Thursday in the lawsuit filed by Illinois and Chicago, which are suing to stop National Guard troops from their state and from Texas being federally activated.
Chicago Mayor Brandon Johnson has called the deployment illegal, unconstitutional, and dangerous, signing an executive order banning ICE agents from operating on city-owned properties.
The deployments raise legal and constitutional questions, as National Guard troops are typically deployed by a state's governor and century-old laws limit the military's use for domestic matters.
Trump has suggested he may invoke the Insurrection Act if federal courts block the deployment of National Guard troops.
In the Oval Office, Trump mentioned Chicago, asserting that if the governor can't do the job, we'll do the job.
