NYPD commissioner: Officers won't help with deportations

The Trump administration's pursuit of unauthorized immigrants may have hit a wall in New York City.

City Police Commissioner James O'Neill told officers in an internal memo that the department would not enforce administrative warrants issued by federal immigration agents.

"It is critical that everyone who comes into contact with the NYPD, regardless of their immigration status, be able to identify themselves or seek assistance without hesitation, anxiety or fear," O'Neill wrote in the memo obtained by ABC News.

"The NYPD does not conduct civil immigration enforcement," the memo to rank-and-file officers said. "Specifically, this department does not enforce administrative warrants issued by Immigration and Custom Enforcement agents or federal immigration judges solely in connection with civil immigration violations."

O'Neill's memo doesn't represent any change in NYPD policy. But in light of a federal plan for more aggressive immigration enforcement, New York City's police commissioner wanted to clarify his department's policy, both to alleviate any concerns in the city's immigrant communities and to remind police officers, sources told ABC News.

Still, the NYPD policy may put the nation's largest police force at odds with the federal Department of Homeland Security, which this week outlined a more aggressive approach to enforcing the nation's immigration laws.

One of two Homeland Security memos issued this week loops other levels of law enforcement into federal immigration efforts, citing a portion of the U.S. Immigration and Nationality Act that "authorizes state or local law enforcement personnel to perform all law enforcement functions ... including the authority to investigate, identify, apprehend, arrest, detain, transport and conduct searches of an alien for the purposes of enforcing the immigration laws."

O'Neill specified in the NYPD memo that while New York City officers "do not enforce administrative warrants" over civil immigration violations, they should detain people who pose danger to the public.

"For example, the NYPD does not arrest or detain individuals for immigration violations such as overstaying a lawfully-issued visa. However, the NYPD does and will continue to honor federal immigration detainers when there is a risk to public safety," it states.