Leading technology-sector bosses denounced President Donald Trump's move Tuesday to end a program that had prevented the deportation of so-called "Dreamers," people who illegally came to the US as children.

Apple chief Tim Cook told employees in an e-mail that "We issue an urgent plea for our leaders in Washington to protect the Dreamers so their futures can never be put at risk in this way again." Cook has tweeted that 250 people who are Dreamers work for Apple.

Facebook founder Mark Zuckerberg took to his social media network, saying Trump's decision was "cruel."

"It is particularly cruel to offer young people the American Dream, encourage them to come out of the shadows and trust our government, and then punish them for it," Zuckerberg wrote.

Attorney General Jeff Sessions announced the decision Tuesday to end President Barack Obama's so-called Deferred Action for Childhood Arrivals (DACA) program, which was implemented in 2012. The program's demise was delayed six months to give Congress a chance to legalize the measure. Sessions said it was "unconstitutional" without Congressional approval. There are as many as 800,000 known Dreamers.

"It's against our values to turn our backs on #DREAMers," Dara Khosrowshahi, Uber's new chief executive, tweeted.

Google chief Sundar Pichai urged Congress "to act now" to protect "our neighbors, our friends, and our co-workers." Microsoft's Brad Smith, the company's chief legal officer, said in a blog post that Congress should act fast.

"We need to put the humanitarian needs of these 800,000 people on the legislative calendar before a tax bill," he wrote. He said Microsoft employed 39 Dreamers.

The list of tech companies blasting Trump's decision goes on and on.

IBM said that it "believes that Dreamers have made a positive contribution to our company and to our economy, and we support bipartisan legislation in Congress to allow them to remain in the United States." Sam Altman, president of Y Combinator, tweeted "I can't believe Trump is doing a political high-wire act with your lives. I'm so sorry. this is cruel." Jack Dorsey, the Twitter chief executive, tweeted that ending DACA "is a crushing blow to those who want to contribute to our future."