Mayor Bill de Blasio is vowing to protect all law-abiding New Yorkers after President Donald Trump signed off on a series of executive orders designed to crack down on undocumented immigrants. Josh Robin filed the following report.

With a visit to the Homeland Security Department, President Donald Trump unleashed a long-expected fight on illegal immigration.

It pits him against a mayor intent on protecting every New Yorker, no matter their immigration status

"We will not deport law-abiding New Yorkers. We will not tear families apart. We will not leave children without their parents," said Mayor Bill de Blasio.

At issue are sanctuary cities, like New York, which shield undocumented immigrants by limiting cooperation between local police and federal immigration agents.

The new president says he wants to crack down on sanctuary cities by getting local law enforcement to do the jobs of immigration agents. 

New York's leaders say that's a non-starter. And they add that even talk of that could jeopardize safety by promoting undocumented New Yorkers to think twice before talking with police. 

"The neighborhood policing, the goal there is, of course, is to keep New Yorkers safe, but it's also to build trust," said Police Commissioner James O'Neill.

"This scares the daylights out of me," said Rep. Joe Crowley, whose district covers parts of the Bronx and Queens.

Trump may have another stick - withholding about $150 million in police funds. 

A document declares, "Sanctuary jurisdictions across the United States willfully violate Federal law in an attempt to shield aliens from removal from the United States. These jurisdictions have caused immeasurable harm to the American people and to the very fabric of our Republic."

Ironically, those funds go, in part, to protecting Trump Tower. 

To some extent, New York has been here before. Two decades ago, Mayor Rudolph Giuliani sued the federal government over a similar issue. 

Federal law had reversed a local rule Giuliani supported. That rule had barred city workers from turning in illegal immigrants seeking services.

In a twist, the President battling Giuliani was Democrat Bill Clinton. Giuliani, of course, went on to champion Trump's presidential bid over Clinton's wife. 

In 1997, a federal judge sided with the federal government, ending the city rule, but not New York's long tradition of the city sheltering immigrants.