Timing and rejection of permission to attack a city

By player266669, in Warrior Knights

Hi there,
I have a qusetion about Warrior Knights, specifically how the rules about permision work.
My group's having some trouble figuring out what to do when permission is NOT granted for attacking a city.
What is the exact timing of when permission is needed to attack a city? Is that before or after I declare my target space? Is the action lost entirely is permission is denied, or may I nominate a different area with my action?
For instance, let's say I reveal my Mobilize Forces action card. I want to start a siege of a neutral city where one of my opponents has a noble present. By rule, I cannot attack that city without first securing his permission. Do I...
A) Ask my opponents if he will give me permission to attack that city, and then if he says yes, I nominate that area and begin my siege?
B) Nominate the area first and announce my intention to attack the city, and then ask my opponent for permsision?
In both cases, if the opposing player does NOT grant me permission, what happens then? Do I get to nominate a different area to move troops into and attack? Or is my ation considered to have failed and is thus lost?
Thank you for any clarification you can provide.