Top executives at companies like Airbnb, AOL, Blue Apron, Casper, Chartbeat, Etsy, Indiegogo, Slack, Trello, Warby Parker, and more have signed a letter that urges the president to rethink the policy that bars people from seven Muslim-majority countries from entering the U.S. “We write out of concern that your recent executive orders will undermine that and send a dangerous message to all immigrants that they are not welcome here,” the letter reads. Uber CEO Travis Kalanick has also signed the letter — just a couple days after his company came under fire for continuing to service John F. Kennedy airport this past Saturday, where thousands were gathered to protest Trump’s ban.

Tech leaders argue that suspending citizens from certain countries — especially those who have legal status — is a decision that threatens “immigrants who are our current and future neighbors, friends, colleagues, customers, and even bosses.”

The letter continues: “Their presence is a crucial ingredient that sets New York City apart and a fundamental reason why we have all chosen to build our careers and companies here.”

Leaders make a point to call out immigrant entrepreneurs who have contributed to some of the biggest tech companies today, including Google, Yahoo, and eBay. “More than half of the companies on the current list of U.S. technology startups valued at $1 billion or more were started by immigrants,” the letter claims. And instead, leaders who have signed the letter believe the president, and others, “should be doing everything in our power to attract these entrepreneurs to the United States.”

The letter comes after some tech leaders — namely execs from Google, Facebook, Apple, Lyft, and Uber — have already spoken out against the order. For reactions outside the tech world, click here.