Washington DC - The Supreme Court dealt a blow to President Donald Trump's immigration crackdown on Tuesday by blocking his deployment of National Guard troops in Chicago.

The conservative-dominated court kept in place for now a lower court order barring the deployment of troops on the streets of the city in the midwestern state of Illinois.

"At this preliminary stage, the Government has failed to identify a source of authority that would allow the military to execute the laws in Illinois," the court said in an unsigned order.

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Three conservative justices – Samuel Alito, Clarence Thomas, and Neil Gorsuch – dissented.

The Republican president has sent National Guard troops to three Democratic-led cities this year – Los Angeles, Washington, and Memphis – but his efforts to deploy soldiers in Portland and Chicago have been tied up in the courts.

The president "activated the National Guard to protect federal law enforcement officers, and to ensure rioters did not destroy federal buildings and property. Nothing in today’s ruling detracts from that core agenda," White House spokeswoman Abigail Jackson said in response to the court's order.

The Democratic governor of Illinois and Democratic mayor of Chicago have strongly opposed the deployment.

After two lower courts blocked Trump from sending troops into Chicago, his administration made an emergency appeal to the Supreme Court.

In his filing with the Supreme Court, Solicitor General John Sauer claimed federal agents in Chicago were being "forced to operate under the constant threat of mob violence."

The court order blocking deployment of the National Guard "improperly impinges on the president's authority and needlessly endangers federal personnel and property," Sauer added.

The Supreme Court rebuff of the appeal was a rare defeat for Trump at the top court, where conservatives hold a 6-3 majority.

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It was not immediately clear how Tuesday's decision would affect the other cases where Democratic-ruled states have challenged Trump's National Guard deployment.

California and Oregon have both filed legal challenges against the Trump administration's extraordinary domestic use of the National Guard.

Trump sent troops to Los Angeles earlier this year to quell demonstrations sparked by a federal crackdown on undocumented migrants.

A district court judge ruled it unlawful, but an appeals court panel allowed the Los Angeles deployment to proceed.

Some 300 National Guard troops remain activated in the Chicago area but are not engaged in operations.