Mayor Rahm Emanuel of Chicago. REUTERS/Henry Romero Mayor Rahm Emanuel of Chicago personally delivered a letter to President-elect Donald Trump asking him to leave one of President Barack Obama's programs in place that shields certain immigrants from deportation.

In a letter on Tuesday, Emanuel and the mayors of 17 other major cities pleaded with Trump to preserve the Deferred Action for Childhood Arrivals program, an executive action of the Obama administration that allows certain immigrants living in the US without permission who arrived when they were children to be shielded from deportation as they pursue higher education or a full-time job.

"Ending DACA would disrupt the lives of close to one million young people, and it would disrupt the sectors of the American economy, as well as our national security and public safety, to which they contribute," Emanuel wrote.

He continued: "We encourage your administration to demonstrate your commitment to the American economy and our security by continuing DACA until Congress modernizes our immigration system and provides a more permanent form of relief for these individuals."

Speaking with reporters after his meeting with Trump on Wednesday, Emanuel said he told Trump "we should embrace them rather than do a bait-and-switch."

He added: "That they were working hard towards the American dream, and that all of us fundamentally believe that these are students, these are also people who want to join the armed forces, they gave their name, their address, their phone number, where they are, they're trying to achieve the American dream — it's no fault of their own their parents came here. They are something we should hold up and embrace."

The mayor also said he presented the case for so-called sanctuary cities, local governments that do not comply with federal requests to detain immigrants living in the US without permission.

Repealing DACA would most likely have enormous consequences for immigrants living in the US illegally. More than 740,000 people have DACA-enabled work permits, while thousands apply for the program each month.

Many Trump supporters are pressuring the president-elect to follow through on his pledge to deport millions of immigrants living in the US illegally. Trump promised throughout the 2016 campaign to roll back Obama's executive actions, and at one point he proposed a deportation force.

But in an interview with Time magazine, Trump appeared to leave the door open to leaving some version of DACA in place.

"I want Dreamers for our children also," Trump said. "We're going to work something out. On a humanitarian basis it's a very tough situation. We're going to work something out that's going to make people happy and proud. But that's a very tough situation."

Emanuel isn't the only major Democratic municipal leader to meet with the president-elect.

Trump sat down with Mayor Bill de Blasio of New York for an hour last month, and he met with Mayor Muriel Bowser of Washington, DC, on Tuesday.