The Democratic mayors of Denver, Chicago, Boston, and New York City were grilled for hours over their so-called sanctuary city policies at a Congressional hearing Wednesday as President Donald Trump pushes his aggressive immigration agenda and threatens to punish cities that don’t comply.

Mayors of four of the largest cities in the U.S. appeared before lawmakers in the U.S. House of Representatives on Wednesday to defend their so-called "sanctuary city" laws, which restrict local officials in helping enforce federal immigration regulations.

The mayors of four so-called “sanctuary cities” faced tough questions from lawmakers about their policies toward immigrants and how they work with Immigration and Customs Enforcement at a House Oversight and Government Reform Committee on Wednesday.