President Donald Trump is planning to sign an executive order Wednesday that would crack down on cities like Portland that refuse to hold undocumented immigrants for deportation, according to The Washington Post and the Associated Press.

Details of Trump's executive order to crack down on "sanctuary cities" remain scarce.

But the AP is reporting that it could involve withholding federal funds from cities that resist the U.S. Immigration and Customs Enforcement agency's request to local law-enforcement to hold undocumented people in jail after an arrest so that feds can deport them.

That's exactly what Trump pledged to do on the campaign trail. He didn't offer specifics then, either.

The executive order puts Trump on a collision course with the city of Portland.

"We will always see ourselves as a sanctuary city, and we will continue to be welcoming to everyone," Wheeler said then. "These are our values."