The troops "will be called into federal service immediately for a period of 60 days to protect US Immigration and Customs Enforcement and other US government personnel who are performing federal functions," Pentagon spokesman Sean Parnell said in a statement.

The planned deployment follows similar moves by Donald Trump to mobilize troops in the Democratic-led cities of Los Angeles and Washington, which the president says was necessary to crack down on crime and protests against his contentious and wide-ranging mass deportation drive.

Oregon filed suit on Sunday to block the National Guard deployment, saying it was motivated by Trump's "desire to normalize the use of military troops for ordinary domestic law enforcement activity," particularly in jurisdictions run by his political opponents.

The state's authorities said there was no need for a National Guard deployment to Portland as -- contrary to Trump's claims -- the protests there against ICE have been small-scale and peaceful.

The suit said the protests typically involve less than 30 people and have not required arrests since mid-June.