Attorney General Jeff Sessions again moved to punish sanctuary cities Thursday by threatening to deny federal crime-fighting funding to four cities struggling with violence if they don't help in the effort to detain and deport people living in the U.S. illegally.

The Justice Department sent letters to the cities, stating they will be ineligible for a new program that aims to root out drug trafficking and gang crime, unless they give federal immigration agencies access to jails and provide advance notice before releasing someone in custody who is wanted on immigration violations.

The four cities are:

Stockton, California

San Bernardino, California

Baltimore, Maryland

Albuquerque, New Mexico

The four cities expressed interest in the Justice Department's new Public Safety Partnership which was launched in June. In the letters, the four cities' police departments were asked to show proof of compliance by Aug. 18 if they wanted to participate in the program.

Currently, 12 cities, none of which are in California, are enlisted in the program. However, Oakland, Richmond and Compton are all participating in pilot operations.

Cities are chosen for the program based on higher-than-average rates of violence and willingness to receive the help and training. Cities that want to be involved have to show they allow communication between police and federal immigration authorities