Dreamers have a powerful and well-heeled ally: Silicon Valley.

American tech leaders are warning President Donald Trump not to end the Deferred Action for Childhood Arrivals (DACA) program. The program, which protects undocumented immigrants who came to the U.S. as children (also known as “Dreamers”) was a policy first announced by the Obama administration in 2012.

Companies including Microsoft and Uber have released their own statements on the matter, after Fox News reported on Thursday that the Trump administration planned to kill DACA. FWD.us, a political advocacy group funded by Silicon Valley money and started by Facebook CEO Mark Zuckerberg, published an open letter to Trump signed by dozens of well-known executives and investors — many of whom employ Dreamers.

The group includes Zuckerberg, Warren Buffett, Netflix’s Reed Hastings, Apple CEO Tim Cook, and Laurene Powell Jobs (widow of the late Apple co-founder Steve Jobs).

“Unless we act now to preserve the DACA program, all 780,000 hardworking young people [in DACA] will lose their ability to work legally in this country, and every one of them will be at immediate risk of deportation,” the FWD.us letter states. “Dreamers are vital to the future of our companies and our economy.”

91 percent of the roughly 800,000 immigrants protected under DACA are currently employed, according to a recent report from FWD.us and the left-leaning Center for American Progress. Trump said earlier this spring that Dreamers should “rest easy,” but USCIS data showed that allegations of criminal activity leading to deportation were up 25 percent from last year — just as Trump appeared to be softening his rhetoric.