The fight over so-called sanctuary cities is flaring up again, pitting the Trump administration against places like New York that have passed measures limiting cooperation with federal agencies over undocumented immigrants. Josh Robin filed the following report.

At a Manhattan conference, lawmakers from across the nation are brainstorming, thinking how they can protect undocumented immigrants in their cities.

"That is the goal, to continue to protect immigrant communities," said City Council Speaker Melissa Mark-Viverito.

At the same moment, at the White House, the Trump administration warns those very places.

"Countless Americans would be alive today, and countless loved ones would not be grieiving today, if these policies of sanctuary cities were ended," said Attorney General Jeff Sessions.

But many leaders in cities like New York say it's the Trump administration that's jeopardizing lives, discouraging people from cooperating with police for fear of being deported.

"So what the federal administration is doing is wreaking chaos in our community, making us less safe in the city of New York, and also making us less safe in this country. So this is a policy that has to be resisted," the City Council speaker said.

Resisted, possibly at a steep cost. The Trump administration is increasingly warning that if local law enforcement agencies don't cooperate with federal immigration officials, they could lose federal funding. 

"A nation without borders is not a nation," Trump said.

It's been a Trump policy, signed in January in an executive order.

Attention lately is heightened after two Maryland high school students, including one here without papers, were accused of raping a classmate in a school bathroom. Henry Sanchez-Milian's lawyer says he is pleading not guilty.

Maryland lawmakers are considering a bill restricting how much local law enforcement can share with federal agencies.

"I would plead with the people of Maryland to understand that this makes the state of Maryland more at risk for violence and crime," Sessions said.

New York's rules limit cooperation with immigration agents. They don't end it. And its backers add the rules aren't just constitutionally sound, but make the city about the safest its been in generations.

Taking away federal funding jeopardizes that, they say. Not to mention, some of that money Trump is threatening to take helps protect his namesake tower.