Mayor Bill de Blasio on Thursday said his administration will seek to shield identifying information about undocumented immigrants in the ID NYC city identification program from federal officials, in the wake of Donald Trump's shocking victory in the presidential campaign.

Immigrants' rights activists have expressed concern that the data in the program, which has been marketed as a way for undocumented immigrants to get a formal piece of identification without endangering their status in the United States, could be be accessed by a Trump administration for the purposes of tracking down and targeting this population.

Speaking at a press conference at City Hall, the mayor said the city would "absolutely" seek to protect the identities of holders of the IDNYC.

Under the terms of the 2014 legislation that created the IDNYC program, the NYC Human Resources Administration, which oversees the program, is required, by the end of calendar year 2016, to review data collected through the program and determine what records should be preserved. The agency retains the right to destroy any records related to proof of identity or residency of IDNYC applicants.

A spokesperson for the mayor's office explained that the IDNYC program does not collect information on the immigration status of applicants.

Asked about broader immigration policy in the city, the mayor said he is committed to shielding the city's estimated 500,000 undocumented immigrants from proposed Trump policies like mass deportations and Trump's threat to withhold federal funds from hundreds of so-called "sanctuary cities" like NYC that protect the undocumented.

"We are not going to sacrifice a half-million people who live amongst us, who are part of our communities, whose family members and loved ones happen to be people in many cases who are either permanent residents or citizens—we're not going to tear families apart," he said. "So we will do everything we know how to do to resist that.

More than 800,000 New Yorkers have signed up for IDNYC since the program launched two years ago.