WASHINGTON (AP) — FBI Director James Comey warned in stark terms Thursday against the push by technology companies to encrypt smartphone data and operating systems, arguing that murder cases could be stalled, suspects could walk free and justice could be thwarted by a locked phone or an encrypted hard drive. Privacy advocates called the concerns exaggerated and little more than recycled arguments the government has raised against encryption since the early 1990s.

Likening encrypted data to a safe that cannot be cracked or a closet door that won't open, Comey said the move by tech companies to protect communications in the name of privacy risks impeding a wide range of criminal investigations.

"We have the legal authority to intercept and access communications from information pursuant to court order, but we often lack the technical ability to do so," Comey said in a Brookings Institution speech.

The speech, which echoes concerns he and others in law enforcement have previously made, comes soon after announcement by Apple and Google that their new operating systems will be encrypted, or protected by coding. While the companies' actions are understandable, he said, "the place they are leading us is one we shouldn't go to without careful thought and debate."

"Encryption isn't just a technical feature. It's a marketing pitch. But it will have very serious consequences for law enforcement and national security agencies at every level," Comey said.

Comey also said the FBI was committed to a "front-door" approach, including through court orders, to intercepting communications. Privacy advocates have long been concerned that that intercept would create an opening for hackers to exploit.

"Whether you call it a 'front door' or a 'back door,' weakening the security of a system to enable law enforcement access also opens that door to foreign governments and criminals," said Christopher Soghoian, principal technologist with the ACLU's Speech, Privacy and Technology Project.