CHICAGO (CBS) — U.S. Attorney General Jeff Sessions on Monday said the Trump administration would block so-called “sanctuary cities” like Chicago from receiving Justice Department grants, and seek to “claw back” existing funds, if they do not begin helping the federal government enforce immigration laws.

“Such policies cannot continue. They make our nation less safe by putting dangerous criminals back on the streets,” Sessions said at a White House press briefing.

Sessions said cities, counties, and states with such sanctuary laws in place would not be eligible to receive Justice Department grants until they certify they are in compliance with federal immigration laws. He also said the Justice Department would take steps to “claw back” any funds that already have been rewarded to such jurisdictions.

“I strongly urge our nation’s states, and cities, and counties to consider carefully the harm they are doing to their citizens by refusing to enforce our immigration laws, and to rethink these policies. Such policies make their cities and states less safe. Public safety as well as national security are at stake, and put them at risk of losing federal dollars,” he said.

In 2012, the Chicago City Council approved an ordinance to protect undocumented immigrants from being held for immigration authorities, unless they have been convicted of a serious crime or are being sought on a criminal warrant. The ordinance also prohibits Chicago police from allowing U.S. Immigration and Customs Enforcement agents from using city facilities for interviews or investigations, and bars officers from replying to ICE inquiries or speaking to ICE officials about someone’s custody status or release date.

New York, Los Angeles, San Francisco, Baltimore, Seattle, Minneapolis, and other major cities across the U.S. also have sanctuary laws limiting cooperation with ICE detainers.

After President Donald Trump took office and threatened to cancel federal funding to cities with such laws, Mayor Rahm Emanuel declared Chicago “always will be a sanctuary city.”

Sessions said the Justice Department will require cities, counties, and states to comply with federal immigration laws in order to receive federal funding through the Office of Justice Programs. He noted the Obama administration also had a policy preventing cities, counties, and states that have such sanctuary laws in place from receiving Justice Department grants.

The attorney general said sanctuary cities make the nation less safe, pointing to a high-profile murder case involving a suspect who was an undocumented immigrant flagged with a federal detainer notice.

In 2015, 32-year-old Kathryn Steinle was gunned down while walking on a San Francisco pier with her father and a family friend. Her accused killer, 45-year-old Francisco Sanchez, is a convicted drug felon who had been deported to Mexico five times cince 1994, and U.S. Immigration and Customs Enforcement had issued a detainer for him three months before Steinle was shot.

However, he was released from the San Francisco jail without notifying ICE of his release, because of the city’s sanctuary policy. Sessions said Sanchez had admitted going to San Francisco because of that policy.

“The American people are not happy with these results. They know that when cities and states refuse to help enforce immigration laws, our nation is less safe. Failure to deport aliens who are convicted of criminal offenses puts whole communities at risk, especially immigrant communities in the very sanctuary jurisdictions that seek to protect the perpetrators,” Sessions said.

Sessions said the Trump administration might take further steps in the future to block sanctuary cities, counties, and states from receiving federal grants.