In an interview with ABC News on Wednesday, Apple CEO Tim Cook spoke out about the tech company’s ongoing privacy fight with the U.S. government, saying the FBI was essentially asking Apple to create “the software equivalent of cancer.”

“This case is not about one phone,” Cook told anchor David Muir. “This case is about the future. What is at stake here is, can the government compel Apple to write software that we believe would make hundreds of millions of customers vulnerable around the world, including the U.S.”

The interview aired just before Apple’s February 26 deadline to respond to the government’s order.

With the help of a federal judge, the FBI is asking Apple to break into the iPhone of one of the suspected shooters in last year’s attack in San Bernardino, California. The tech company has resisted the order, saying that creating that software would set a dangerous precedent that threatens users’ privacy rights and expands government authority.

“We think [the software is] bad news to write,” Cook said on Wednesday. “We would never write it, we have never written it, and that is what is at stake here…. If a court compels Apple to write this piece of software, to place a backdoor in the iPhone, we believe it does put hundreds of millions of customers at risk.”

Cook continued: