British Prime Minister Theresa May and French President Emmanuel Macron are joining forces in order to crack down on tech companies, ensuring they step up their efforts to combat terrorism online.
Britain and France face similar challenges in fighting homegrown Islamist extremism and share similar scars from deadly attacks that rocked London, Manchester, Paris and Nice.
May traveled to Paris on Tuesday to hold talks on counterterrorism measures and Britain's departure from the European Union.
She said major internet companies had failed to live up to prior commitments to do more to prevent extremists from finding a "safe space'' online. Macron urged other European countries, especially Germany, to join the effort to fight Islamist extremist propaganda on the Web.
The campaign includes exploring the possibility of legal penalties against tech companies if they fail to take the necessary action to remove unacceptable content, May said.
After the Islamic State group recruited hundreds of French fighters largely through online propaganda, France introduced legislation ordering French providers to block certain content, but it acknowledges that any such effort must reach well beyond its borders. Tech-savvy Macron has lobbied for tougher European rules, but details of his plans remain unclear.
Britain already has tough measures, including a law known informally as the Snooper's Charter, which gives authorities the powers to look at the internet browsing records of everyone in the country.
Among other things, the law requires telecommunications companies to keep records of all users' Web activity for a year, creating databases of personal information that the firms worry could be vulnerable to leaks and hackers.