CHICAGO — Chicago police, federal agents and prosecutors launched an initiative Friday aimed at stemming the flow of illegal firearms in the city as part of efforts to curb rampant gun violence that President Donald Trump says is at “epidemic proportions.”

Trump’s remark on Twitter came ahead of an announcement by Chicago police and the Bureau of Alcohol, Tobacco, Firearms and Explosives about the formation of the Chicago Crime Gun Strike Force.

Mayor Rahm Emanuel’s office said an additional 20 ATF agents have been sent to Chicago. Tim Jones, the ATF’s special agent in charge of the strike force, said the agents will be assigned permanently to the city.

State police, intelligence analysts, and state and federal prosecutors will target illegal guns and repeat gun offenders, Chicago police said. Superintendent Eddie Johnson said in a statement that “we are foundationally changing the way we fight crime in Chicago.”

Trump tweeted Friday morning that “Crime and killings in Chicago have reached such epidemic proportions that I am sending in Federal help.” In January, he warned Chicago about its high number of homicides, saying on Twitter that he is ready to “send in the Feds.”

Adam Collins, spokesman for Mayor Rahm Emanuel, said the city wants the assistance.