US President Donald Trump on Wednesday signed a memo threatening to cut federal funds to US cities that have seen a series of protests over the past few months. The "lawless" cities include Seattle, Portland, New York, and Washington DC.

"My Administration will not allow federal tax dollars to fund cities that allow themselves to deteriorate into lawless zones," said the memo released by the White House.

It instructed Attorney General William Barr to work on jurisdictions that "permitted violence and the destruction of property to persist and have refused to undertake reasonable measures."

In a separate interview with CNN, Barr said the Justice Department was looking into the movements of the protest movement antifa.

"I've talked to every police chief in every city where there has been major violence and they all have identified antifa as the ramrod for the violence," Barr said. "They are flying around the country. We know people who are flying around the country."

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Trump has been using the "law and order" message to appeal to some white supporters, and antifa, a loosely organized left-wing movement against authoritarianism and racism, is a regular target for the president.

Leaders from the cities in question have denounced the president's threat of defunding. New York Governor Andrew Cuomo tweeted that Trump was trying to "punish" New York City.

"He is not a king. He cannot 'defund' NYC," Cuomo said. "It's an illegal stunt."

Portland Mayor Ted Wheeler wrote on Twitter: "Trump threatens to withdraw federal funds, possibly including health, education and safety net dollars Americans need to get through the pandemic and economic crisis."Again, he targets cities - including ours - with democratic Mayors, which he calls 'anarchist jurisdictions.'"