Mayors from 25 U.S. cities met in New York City for a summit to discuss groundwork for implementing President Obama's executive action to provide immigration relief to millions of undocumented people nationwide.

The group worked out coordinating and sharing expertise, and strategies to push for immigration reform.

"The President's plan to act on immigration reform is crucial to creating a more just country, and the federal government is depending on cities to implement the plan. It is critical that we get it right," said Mayor Bill de Blasio from Gracie Mansion on Monday. "Mayors are in the trenches and see firsthand the need for comprehensive immigration reform."

The summit included mayors and staff representing 25 cities: Atlanta, Boston; Buffalo; Charlotte; Dayton; Harford; Houston; Jersey City; Los Angeles; Louisville; Madison; New Haven; Newark; Philadelphia; Pittsburgh; Providence; Salt Lake City; San Francisco; San Juan; Santa Fe; Schenectady; Seattle; Syracuse; Tacoma; and Washington, D.C.

Mayor de Blasio said the consensus in the summit was that reform is closer because of the president's executive action and, while there will be backlash, they think more people will come to realize larger reform is needed.

"[T]here's almost 12 million Americans who are faced with all the challenges of being undocumented, and who live lives that just aren't as full and complete as they could be, and so many of them are our constituents, and we know the president's action is going to change things for so many of them," said de Blasio.

He said some cities have been pioneering municipal ID programs in New York and New Haven, and many cities have worked to limit ICE detainers to make sure families are kept whole.  

"Our immigration system is broken. Every day Congress delays action on meaningful reform further hurts families and affects our economy. These issues impact our cities each day, which is why I am proud to join Mayor de Blasio and others to support the President's executive order and implement change now. We can no longer afford to wait," said Providence Mayor Angel Taveras.

The summit discussions led to the Mayor's challenge, a five-point plan around the implementation of Obama's immediate immigration relief and structure to build for greater reform. That will involve mayors reaching out to other mayors to support the program, a social media campaign to galvanize support, a day of action in January and a Mayoral Lobby Day on Capitol Hill in February.

"Five million people -- that's absolutely extraordinary. We stand by the president for taking such bold action and I think the consensus of the room is that this is the beginning," de Blasio said. "The fact that we went from zero to 5 million with the stroke of a pen is a transcendent, historical moment for this country."

The Cities United for Immigration Action coalition, launched two weeks ago, includes an additional 18 cities who were not able to join the summit.

"As the son of immigrant parents, this issue is personal to me. The President's bold action on immigration has set the course, and now we must follow through," said San Francisco Mayor Ed Lee. "We're going to take this opportunity up very seriously, very vigorously and very broadly."