How can I prevent monsters from being attacked in scripts?

I want to implement a system where, when attacking a monster, a dialogue appears, essentially making the monster offer a quest. I need to be able to interact with this monster, but not attack it. That is, I don't just want to block access to it so that I can't even hover the cursor over it, but rather make it so that I can approach it, but combat doesn't start. After all, I need to be able to somehow complete the quest with it later.