Undocumented Chicago students "have nothing to worry about," Mayor Rahm Emanuel said Tuesday. View Full Caption Twitter/@ChicagosMayor

GAGE PARK — Undocumented immigrants known as "Dreamers" — allowed to stay in the U.S. under a program established by President Barack Obama — are facing deportation after the Trump administration announced Tuesday it is phasing out the program.

In Chicago, Mayor Rahm Emanuel was quick to assure students in the program and living in the city that they had nothing to worry about despite the end of the administration's Deferred Action for Childhood Arrivals program. He declared Chicago a "Trump-free zone."

On the first day of classes for Chicago Public Schools, the mayor visited Solorio Academy High School, a Gage Park school at 5400 S. St. Louis Ave. where nearly a third of students are undocumented, school officials said.

Emanuel said the Trump administrations's decision "strikes a blow against our core American values and is an affront to basic human decency."

"The United States is a nation of immigrants, not a country that tears families apart or deports children who have placed their faith in the promise of America," Emanuel said. "I know countless Dreamers in Chicago who are talented, hardworking and dedicated to their families and the only home they have ever known. Not only will Chicago continue to welcome Dreamers, we will pursue every legal option to protect our children, defend our immigrant communities and uphold the enduring promise of the American dream."

Roman Catholic Archbishop of Chicago Blase Cupich called the president's decision "heartless."

"The Dreamers are now left in a six-month limbo, during which Congress is supposed to pass comprehensive immigration reform, a feat they have been unable to achieve for a decade," Cupich said in a statement. "In fact, this inability to agree on a just immigration system led President Obama to sign the executive order protecting minor children brought to this country by their parents."

Congress "must now act decisively and swiftly," Cupich said.

"They must be guided by compassion and respect for human dignity, and honestly consider the substantial evidence that deporting these young Americans would do great economic harm to the states where they reside," Cupich said.

Former President Barack Obama, in a lengthy statement posted on social media, called Trump's decision "wrong because (DACA participants) have done nothing wrong." The announcement breaking from the longheld tradition that former presidents refrain from directly criticizing the current occupant of the Oval Office.

To target hopeful young strivers who grew up here is wrong, because they’ve done nothing wrong. My statement: https://t.co/TCxZdld7L4 — Barack Obama (@BarackObama) September 5, 2017

No new applications for the two-year-long protected status will be processed by the Trump administration, U.S. Attorney General Jeff Sessions said, referring to participants — who were brought to the United States as children by their parents — as "illegal aliens."

Sessions said the program was unconstitutional and — without presenting evidence during his brief statement to reporters — that Dreamers had "denied jobs to hundreds of thousands of Americans."

Current program participants will be allowed to continue working until their permits expire. Those whose permits expire by March 5, 2018, will be permitted to apply for two-year renewals as long as they do so by Oct. 5, officials said.

That would give Congress six months to enshrine the program into law before deportations would be allowed to start, officials said.

U.S. Rep Luis Gutierrez (D-Chicago) said he would lead the fight in Congress against any spending plan that does not protect Dreamers. Unless Congress approves a new spending plan by the end of the month, the federal government will partially shut down.

"Immigrant youth, immigrant families, and our allies in all sectors of American life are here to stay, regardless of the president’s mass deportation fantasies and objectives," Gutierrez said. "Americans will not let this president dictate the fate of the immigrants who have placed so much trust in their country."

U.S. Sen. Dick Durbin (D-Illinois) said Trump previously "looked me in the eye and said: 'Don't worry. We are going to take care of those kids.'"

But Sessions' statement Tuesday "was cold, harsh, threatening, and showed little respect, let alone love, for these Dreamers," Durbin said.

"Families will be torn apart, and America will lose many of our best and brightest unless Republicans join with Democrats to right this wrong immediately," Durbin said.

U.S. Sen. Tammy Duckworth (D-Illinois) said Trump's decision was "a gut-wrenching betrayal of American values."

"To end a program that allowed these patriots to come out of the shadows and more fully contribute to this country is irresponsible and heartless," Duckworth said.

ACLU of Illinois Executive Director Colleen Connell said Trump's decision was "terribly cruel" for the nearly 20,000 young people in Illinois who have legal status thanks to DACA.

Immigration and Customs Enforcement agents aren't allowed into Chicago Public Schools without a warrant, Emanuel reminded students Tuesday.

At Trump Tower in New York City in December, in Emanuel's first meeting with then President-elect Trump after the election, he gave Trump a letter signed by 14 mayors from across the country urging him to continue the Deferred Action for Childhood Arrivals program. Getting rid of the program will harm the city's economy, he said.

The city's website refers to a study by the think tank the Center for American Progress concluding that ending DACA would force 36,867 Illinois out the state economy at a annual cost of $2.2 billion from the national gross domestic product.

"Chicago will always be a welcoming city," Emanuel said, adding that the city will continue to offer free tuition at City Colleges of Chicago to any graduate of Chicago Public Schools with a B average.

Emanuel has repeatedly clashed with Trump and Sessions on issues related to immigration.

Emanuel said it was unconscionable for the Trump administration to consider "going after" people who were brought here as children by their parents without U.S. government permission.

A rally to protest the end of DACA is set for at 5:30 p.m. Tuesday at Federal Plaza, 230 S. Dearborn St.