A political standoff over US President Donald Trump's plan to crack down on crime and illegal immigration in Chicago intensified on Sunday as a top administration official promised to deploy more federal officers and the Democratic governor of Illinois portrayed Trump as a threat to democracy.

Homeland Security Secretary Kristi Noem told CBS News' "Face the Nation" that US Immigration and Customs Enforcement operations in Chicago and other parts of the country would be bolstered, but declined to provide details. Noem said Trump would make any decision to deploy National Guard troops.

On the same programme, Illinois Governor JB Pritzker said Trump wanted to deploy troops so that he could halt or manipulate US midterm elections in 2026.

"He'd like to stop the elections in 2026 or, frankly, take control of those elections," Pritzker said. "He'll just claim that there's some problem with an election, and then he's got troops on the ground that can take control."

White House spokeswoman Abigail Jackson criticised Pritzker for not doing more to deal with crime.

"Chicago’s residents would be much safer if Pritzker actually did his job and addressed his crime problem instead of trying to be a Resistance Lib hero," Jackson said in a statement.

Trump and top officials have said in the past week that Chicago would soon be a target for the Republican president’s efforts to tackle crime and illegal immigration.

Trump for years has criticised crime in Chicago, a Democratic stronghold, although city figures show most categories of violent crime have dropped this year.

Earlier this month, Trump kicked off an aggressive public safety campaign in Washington, DC, deploying National Guard troops, flooding streets with federal officers, and federalising the city police department.

The surge has generated political and community pushback in DC, a federal district where Trump wields exceptional power.

Chicago Mayor Brandon Johnson, a Democrat, issued an executive order on Saturday that said local police would not assist with National Guard or other federal operations. (Reuters)