BERLIN (AP) — Germany’s justice minister is criticizing plans for Facebook to combine its instant-messaging services after a meeting with CEO Mark Zuckerberg, but is offering a wary welcome to his call for more encrypted messaging.

Minister Katarina Barley said in a written statement after meeting Zuckerberg on Monday that plans to combine WhatsApp and Instagram Direct with Facebook’s core Messenger app raises “very significant cartel law and data protection law questions.”

Still, she said “it is worth discussing some of Mark Zuckerberg’s ideas,” adding that more encrypted private messaging is a good thing and suggesting it could save lives in authoritarian systems. But Barley stressed that “Facebook must not become a gigantic, self-contained communication space that concentrates yet more market and data power.”

Zuckerberg unveiled Facebook’s plans last month.