They're not ready to announce anything. Attribution is hard and that's part of the discussion. It's easy to pretend to be a nation-state setting up in a different nation-state. We can't tell where the attack is actually coming from. We very often cannot tell where the attack is coming from, because people are very good at espionage and hiding themselves, pretending to be somebody else.
On February 20th, 2019. See this statement in context.