President Donald Trump’s controversial executive order, which suspends refugee arrivals and imposes tough controls on travelers from seven Muslim countries, has irked several tech companies in the United States.

The order, signed in by Trump Friday, is meeting with stiff opposition from the Silicon Valley, with most tech company executives who met Trump when he was president-elect criticizing the ban on immigration.

Apple CEO Tim Cook, who Trump is trying to convince to move iPhone production to the U.S., has written a letter to the company’s legal, security and HR teams to support employees affected by the ban.

"Apple would not exist without immigration, let alone thrive and innovate the way we do," Cook wrote.

Reed Hastings, the CEO of Netflix said on Facebook: “Trump’s actions are hurting Netflix employees around the world, and are so un-American it pains us all. Worse, these actions will make America less safe (through hatred and loss of allies) rather than more safe.”

Uber CEO Travis Kalanick, who was blamed Saturday for cozying up to Trump, also uploaded his letter to Uber employees on Facebook.

“While every government has their own immigration controls, allowing people from all around the world to come here and make America their home has largely been the U.S.’s policy since its founding. That means this ban will impact many innocent people — an issue that I will raise this coming Friday when I go to Washington for President Trump’s first business advisory group meeting,” he wrote.

Even Tesla CEO Elon Musk, who is on Trump’s policy panel tweeted: “The blanket entry ban on citizens from certain primarily Muslim countries is not the best way to address the country’s challenges.”

Many tech companies have stepped in to help affected employees, with Uber extending financial support to drivers affected by the ban, while Microsoft is offering legal help to employees affected by the ban.

Trump met with leaders of tech companies including Tim Cook, Amazon's Jeff Bezos and Alphabet's Larry Page on Dec. 14, as president-elect to discuss job creation in the U.S. Expressing admiration for the work done by them, he offered the companies direct support.

"There’s nobody like you in the world. There’s nobody like the people in this room and anything we can do to help this go along, we’re going to be there for you. You’ll call my people, you’ll call me, it doesn’t make any difference. We have no formal chain of command around here,” he told the tech industry leaders.

But the immigration issue looks like it is taking matters down a different course, with most tech critical of the policy. Many tech companies have staff made up of immigrants from around the world. For example, companies such as Microsoft and Google have Indian-origin CEOs. By banning immigrants from 7 Muslim countries, Trump is affecting the working of these companies; Google, for instance, has 178 employees from the listed countries.

Trump's policy decisions could affect the U.S. tech industry significantly, possibly prompting some of them to consider other countries to move operations to. For one, they could set up innovation centers outside the U.S., where they won’t face such restrictions on hiring.