Apple CEO Tim Cook on Wednesday urged for government action to protect undocumented immigrants brought to the U.S. as children, calling their plight the “biggest issue of our time.”

“These people, if you haven’t met them — at Apple we have many people who came to the U.S. when they were two years old,” Cook said at the Bloomberg Global Business Forum. “They didn’t exactly make a decision to come.”

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Some of these immigrants were shielded from deportation under the Obama-era Deferred Action for Childhood Arrivals (DACA) program, which the Trump administration announced earlier this year it was planning to phase out.

“They came here, they only know our country,” Cook said. “This is their home. They love America deeply.”

Cook is among a growing number of Silicon Valley leaders who have criticized President Trump’s decision to end the program. Microsoft president Brad Smith called on Congress to prioritize legislation to protect DACA recipients over tax reform.

Trump and Democratic leaders have been in talks about reviving legislation to protect young immigrants.

Cook said on Wednesday that he sees immigration more as a moral issue than a political one.

“I am personally shocked that there is even a discussion of this,” he said.