SAN FRANCISCO (CBS SF) — Using a press conference about a crackdown on MS-13 gang members in the U.S. as a backdrop, Acting Immigration and Customs Enforcement Director Thomas Homan took aim Thursday at sanctuary cities like San Francisco and several other Bay Area communities.

Homan said sanctuary city policies are a “magnet” for crimes, particularly the smuggling of illegal aliens into the country.

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“I’ll say it once again — sanctuary cities are a criminal’s best friend,” Homan told the White House press corp. “If you are an alien smuggler and you are smuggling people illegally into this country, that’s one sales pitch. We can get you to a sanctuary city where that city will help shield you from immigration.”

Homan said there will be no safe haven for undocumented immigrants and that additional resources will be use to target them in sanctuary cities.

“If you are in a sanctuary city, that’s where we are going to send additional resources to look for you at your home, your place of employment,” he said. “We are going to enforce the law.”

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Homan also called for cooperation from cities like San Francisco to crack down on illegal immigration.

“Sanctuary cities need to help us to keep the city safe,” he said. “Sanctuary cities not only endanger the public’s safety, but they endanger my law enforcement officers because when we can’t get a violent alien out of county jail, it means that one of our officers will be forced to knock on a door which anyone in law enforcement knows that is one of the most dangerous things to do.”

Homan said that gang members like those involved in MS-13 “walk out of country jails everyday.”

“That’s what we need to change,” he said.

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“If we send the message that if you get in the country and get by the Border Patrol and don’t get arrested by local law enforcement for another crime — then no one is looking for you — that is a magnet, that is a pull factor,” Homan told reporters. “We’ve got to stop that messaging. We got to tell people it’s not alright to violate the laws of this country. You can’t want to be a part of country and not respect its laws.”