The Department of Homeland Security (DHS) has requested 20,000 National Guard troops to help with the Trump administration’s immigration enforcement, a DHS official confirmed to The Hill Thursday.

The department requested the Guard members from the Pentagon “to help carry out the President’s mandate from the American people to arrest and deport criminal illegal aliens,” DHS Assistant Secretary Tricia McLaughlin said in a statement.

A Defense official also told The Hill that the Pentagon “received a request” this week but was not able to share the contents because planning is in the initial stages and predecisional. 

The New York Times first reported on the request and was told Pentagon lawyers were reviewing it along with “interior immigration enforcement.”

It is unknown what role National Guard members would take in the immigration crackdown, such as whether they would be involved in rounding up and arresting people for deportation or just transportation or security. 

It’s also unclear whether state governors would have to approve the plan or if President Trump would move to federalize the National Guard to take control of its troops. The last time the U.S. government did so was in 1992 during the Los Angeles riots, sparked by the police beating of Rodney King.

The plan was quickly bashed by Democratic lawmakers including Sen. Tammy Duckworth (D-Ill.), who said she was “deeply disturbed” by Trump’s “abuse and misuse” of the U.S. military.

“Trump’s DHS is asking for 20,000 National Guardsmen to assist with immigration enforcement within our nation’s borders—something they’ve never been asked to do before and that is not part of the National Guard’s mission,” she said in a statement. 

“Not only does this undermine readiness and our national security, it also means Trump is testing the limits of how he can misuse our military against the American people,” Duckworth added. “No one should believe that he will stop at immigrants if this plan moves forward.”

National Guard troops at the state level have previously been asked to assist in deportations — notably in Texas, where Republican Gov. Greg Abbott in February gave his Guard members the authority to arrest migrants — but this would mark the first time Guard troops at the national level have been asked to do so.

The DHS request comes after Trump last week ordered the department to increase its deportation force by 20,000 officers, pulled from state or federal agencies.

The commander in chief heavily campaigned on minimizing illegal immigration and removing immigrants in the United States without legal status, promising “mass deportations.”

Last month, Trump authorized the military to take control of federal land stretching across three states at the southern border and designate it as “National Defense Areas” to assist in implementing his immigration crackdown. The move gave the military a more direct role in interacting with immigrants at the border, as it was given the authority to detain and search immigrants lacking certain documentation in New Mexico.

In the past decade, National Guard troops have traditionally supported law enforcement agencies with immigration issues at the border via logistics, surveillance, security and setting up temporary barriers or fencing, and they were not meant to come into contact with individuals crossing into the United States.