New York CNN Business  — 

US Attorney General William Barr and senior government officials from the UK and Australia are formally asking Facebook to give up on its plan to encrypt user messages across its platforms.

In an open letter to Facebook (FB) CEO Mark Zuckerberg made public Thursday, the officials wrote that while “law abiding citizens have a legitimate expectation that their privacy will be protected,” effective encryption can hinder “our law enforcement agencies’ ability to stop criminals and abusers in their tracks.”

The letter was signed by Barr, acting US Secretary of Homeland Security Kevin McAleenan, UK Home Secretary Home Priti Patel, and Australian Minister for Home Affairs Peter Dutton.

The encryption debate, which pits tech companies that want to ensure user communications are private and secure against law enforcement’s desire to access such messages, is decades old.

Some messaging services, such as Facebook’s WhatsApp, utilize end-to-end encryption by default, meaning that only the individual devices an account is on — and not even the company that hosts the message — will have the keys to decrypt a conversation.

Barr revived the issue in July, calling tech companies’ embrace of end-to-end encryption “dangerous” and “unacceptable.”

“We respect and support the role law enforcement has in keeping people safe,” a Facebook spokesperson said in a statement provided to CNN. “We strongly oppose government attempts to build backdoors because they would undermine the privacy and security of people everywhere.”

Civil liberties groups also resoundingly oppose such measures. “It’s a staggering request. Despite claiming to ‘support strong encryption’ these law enforcement officials are asking for the ability to access the text of all communications,” said Andrew Crocker, a senior staff attorney at the Electronic Frontier Foundation. ‘It would fundamentally compromise the security and privacy of encrypted communications on Facebook.”

CNN’s Donie O’Sullivan and Evan Perez contributed to this report