Former President Barack Obama on Tuesday responded to President Donald Trump’s decision to end the Deferred Action for Childhood Arrivals (DACA) program and called on Congress to “step up” and help those granted legal protection under the program.

Obama said in a Facebook post that undocumented immigrants brought to the United States as children, who the program grants legal protection, “are Americans in their hearts, in their minds, in every single way but one: on paper.”

He said that he spent “years” as president asking Congress to send him a bill that would give such immigrants a path to citizenship.

“That bill never came,” Obama said. “And because it made no sense to expel talented, driven, patriotic young people from the only country they know solely because of the actions of their parents, my administration acted to lift the shadow of deportation from these young people.”

He said his administration “did so based on the well-established legal principle of prosecutorial discretion, deployed by Democratic and Republican presidents alike,” pushing back on Trump’s claim that Obama overextended executive authority by implementing the program.

“To target these young people is wrong – because they have done nothing wrong. It is self-defeating,” Obama said. “And it is cruel.”

He said Trump’s decision was not “required legally” but rather “a political decision, and a moral question.”

“Now that the White House has shifted its responsibility for these young people to Congress, it’s up to Members of Congress to protect these young people and our future,” Obama said. “I join my voice with the majority of Americans who hope they step up and do it with a sense of moral urgency that matches the urgency these young people feel.”