The Trump administration said on Friday it would ask companies to pay $100,000 per year for H-1B worker visas, prompting some big tech companies to warn visa holders to stay in the U.S. or quickly return.

The change could deal a big blow to the technology sector that relies heavily on skilled workers from India and China.

Since taking office in January, Trump has kicked off a wide-ranging immigration crackdown, including moves to limit some forms of legal immigration. The step to reshape the H-1B visa program represents his administration’s most high-profile effort yet to rework temporary employment visas.