Mayor Rahm Emanuel on Monday added his formidable voice to the parade of those condemning President Donald Trump’s controversial immigration policy of separating children from their parents at the U.S. border.

Emanuel chose to tee off on his favorite political target — Donald Trump — after welcoming Walgreens to Chicago’s still-under-renovation old main Post Office.

“I think it is an absolute mistake what is happening on our border of the United States,” the mayor said as Walgreens employees assembled in the building’s ornate lobby broke out in applause.

“I know what America stands for. As an American, I believe in America and its values. And separating a parent from their child who is only trying to bring their child to a better tomorrow is not who we are. Not what we believe in.”

Emanuel has spent the last two years in a running legal and political battle against Trump, who has used Chicago as his favorite punching bag.

The no-risk battle against a Republican president in this overwhelmingly Democratic city is tailor-made to rebuild Emanuel’s national image and bolster his popularity among Chicago Hispanics most threatened by Trump’s immigration policies, and by the president’s threat to cut off funding to sanctuary cities.

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The gut-wrenching scenes of children being ripped away from their parents at the border has opened yet another front in the running battle.

And the mayor made it a point to note that it has brought together prominent people from opposite sides of the political spectrum.

“The only thing I can ever say complimentary of Donald Trump is [that] he brought people from diverse views and backgrounds — from Laura Bush to myself — to agree that he is wrong. And absolutely wrong for America’s future,” the mayor said.

Children hold signs at demonstration outside Immigration and Customs Enforcement offices in Florida

Children hold signs during a demonstration in front of the Immigration and Customs Enforcement offices in Miramar, Fla. The Trump administration’s move to separate immigrant parents from their children on the U.S.-Mexico border has turned into a full-blown crisis, drawing denunciation from the United Nations, Roman Catholic bishops and countless humanitarian groups. | AP Photo/Wilfredo Lee

“What is happening today in the name of America is not the America we believe in.”

The mayor never mentioned First Lady Melania Trump, but he could have.

On Sunday, the First Lady’s communications director Stephanie Grisham told CNN that Mrs. Trump “hates to see children separated from their families and hopes both sides of the aisle can finally come together to achieve successful immigration reform.”

“She believes we need to be a country that follows all laws, but also a country that governs with heart,” Grisham was quoted as saying.

The mayor’s broadside came one day after retiring U.S. Rep. Luis Gutierrez compared Trump’s actions to the tactics Adolf Hitler used in Nazi Germany.

“He is using fear of the immigrant … he is using prejudice. … You know who did that?” Gutierrez asked members of Lincoln United Methodist Church in Pilsen.

“That’s the way you got fascism in Germany. That’s the first thing the Nazis did in Germany. They said, ‘Get rid of all those foreigners, and let’s make this a German nation,’” said Gutierrez, a son of Puerto Rican immigrants.

“So understand that blaming other people for your woes is an old strategy, and that’s exactly what the president of the United States is doing,” he said.

Nearly 2,000 children were separated from their families over a six-week period in April and May after U.S. Attorney General Jeff Sessions announced a new “zero-tolerance” policy that refers all cases of illegal entry for criminal prosecution.

U.S. protocol prohibits detaining children with their parents because the children are not charged with a crime and the parents are.

Officials in the Trump administration have said the “zero tolerance” strategy is a deterrent to ebb the flow of migrant families across the border.

Trump said last week, “I hate the children being taken away.” He has portrayed Democrats at the roadblock standing in the way of comprehensive immigration reform.

Also on Monday, Emanuel said he has no qualms about his decision to pull Soldier Field from the 2026 World Cup bid jointly organized by the soccer federations of the U.S., Canada and Mexico.

“We have brought a lot of sporting events [to Chicago]: the NHL draft, the NFL draft, the NBA All-Stars and other soccer and rugby games, sailing. But unlike other sporting events, they wanted a blank check,” the mayor said.

“I am not having the taxpayers underwrite this sporting event and allow you to charge, like a credit card with an unlimited account on the taxpayers. We’d love to have the sporting events. We’re a great soccer town with all the communities from around the world and the United States that love soccer. But they wanted a blank check from the taxpayers and I told them, `Absolutely not.’”