WASHINGTON • The United States, the United Kingdom and Australia have called on Facebook to not go ahead with end-to-end encryption across its messaging services unless law enforcement officials have backdoor access, saying encryption hindered the fight against child abuse and terrorism.

The US and UK also signed a special data agreement that would fast-track requests from law enforcement to technology companies for information about the communications of terrorists and child predators. Law enforcement could get information in weeks or even days instead of the current wait of six months to two years.

In an open letter to Facebook and its chief executive Mark Zuckerberg, the three allies said that while they supported strong encryption, it was necessary to balance the need for secure data with public safety. They urged Facebook and other companies to "enable law enforcement to obtain lawful access to content in a readable and usable format".

The letter was signed by US Attorney-General William Barr, UK Secretary of State for the Home Department Priti Patel and Australian Home Affairs Minister Peter Dutton.

Facebook said in a statement that it strongly opposes "government efforts to build backdoors", which it said would undermine privacy and security. Mr Zuckerberg said on Thursday that he had been aware of child exploitation risks before announcing his encryption plan and acknowledged that it would reduce tools to fight the problem.

Speaking in a livestream of the company's weekly internal question-and-answer session, he said he was "optimistic" that Facebook would be able to identify predators even in encrypted systems, using the same tools it used to fight election interference.

He also suggested the company might further limit the ways adults can interact with minors on Facebook's platforms.

REUTERS