Apple CEO Tim Cook in an interview that will air on Thursday evening said the government is asking his tech company to make the “software equivalent of cancer” in order to combat terrorism.

“The only way to get information, at least currently, the only way we know, is to write a piece of software that we view as sort of the software equivalent of cancer,” Cook said in an interview excerpt. “We think it’s bad news to write, we would never write it, we have never written it. And that is what is at stake here.”

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The FBI has called on Apple to crack the iPhone of Syed Farook, one of the attackers in the San Bernardino, Calif., massacre that left 14 dead in December.

But the tech giant has refused to comply with authorities, arguing such a program would compromise the privacy of all iPhone users.

Cook said there is a “trade-off” between public safety and privacy.

“I think safety of the public is incredibly important — safety of our kids, safety of our family is very important,” he said. “The protection of people’s data is incredibly important, and so the trade-off here is we know that doing this could expose people to incredible vulnerabilities.”

“David, some things are hard, and some things are right, and some things are both. This is one of those things,” he added.

The full interview will air on ABC's "World News Tonight with David Muir."