i don't think theres any actual way of stopping a unit attack without manipulating alliance status, so you're kinda stuck on options. You might be able to by disabling/enabling units, but i'm not so knowledgable about that, so you're gonna have to wait.
now that i think about it, if its a one hit kill lurker, you could blind it. since it can't see anything until someone attacks it, it won't retailiate because its already dead