What happens if you attempt to create a formal alliance with AI?

I’m in the middle of 4 players and 1 AI who is rapidly expanding. I’m not sure exactly how aggressive they are, but if I could form an alliance I’m curious on if it would be a waste of 150 or if I could safely block off a threat with an alliance with the AI. Has anyone had experience with this yet?

Really a waste of $150, AI will rapidly expand, but it will only expand to unclaimed stars. It won’t attack, yet. Someday Jay will change that though. The AI, once it has no unclaimed stars to claim, will just move ships around, trying to balance the number on each star. You can use that to nab a star it has just moved some ships off of, unless it has more coming in…