Attorney General Jeff Sessions announced Monday that sanctuary cities and counties are in danger of losing grants and funding from the Department of Justice if they do not comply with federal immigration officials such as Immigration and Customs Enforcement (ICE).

"[Immigration] laws require us to properly remove aliens when they are convicted or detained for certain crimes," Sessions said at the daily White House press briefing. "Unfortunately, some states and cities have adopted policies that are designed to frustrate this enforcement of immigration laws."

Crime rates across the nation have gone up due to a widespread tolerance of undocumented immigrants, Sessions said.

"When cities and states refuse to help enforce immigration laws, our nation is less safe," he said. "Countless Americans would be alive today and countless loved ones would not be grieving today if these policies of sanctuary cities would end."

Sessions explained what states, counties and cities would have to do to continue receiving DOJ grants and funding for law enforcement.

"The Department of Justice will require that jurisdictions seeking or applying for Department of Justice grants to certify compliance with [U.S. Code] 1373, and as a condition of receiving those awards," he said.

U.S. Code 1373 outlines how state agencies must not "restrict any government entity or official from sending to, or receiving from, the Immigration and Naturalization Service information regarding the citizenship or immigration status, lawful or unlawful, of any individual."

Lt. Gov. Gavin Newsom of California commented on Facebook that the alleged increase in crimes in sanctuary cities is not true.

"On average, 35.5 fewer crimes are committed per 10,000 people in sanctuary counties," he said. He also listed figures that show the unemployment and poverty rate are lower. "Before you take away our funds, I suggest you take a look at the facts, Mr. Attorney General."

Niels Frenzen, clinical professor of law and director of the immigration clinic at USC said it's clear that the Trump administration is planning to act on the threats. "What is much less clear is what legal authority the federal government has to carry out some of the threats," he added.

Other government officials including California Senate leader Kevin de Leon and Rep. Juan Vargas of San Diego spoke out against the measures Sessions described.

De Leon described Sessions' statements as "unconstitutional threats and blackmail," while Vargas discussed how Trump's harsh immigration policy has led to a decrease in reported crimes by immigrants.

Reach staff reporter Simrin Singh here.