How to force AI to siege your cities

For role-playing purpose, I often tried to force enemy armies to lay siege to my cities, defended by a punch of men. But I never accomplished my goal, even by leaving the city _undefended_ (it's a nonsense that a full stack enemy army would turn and go away if there is a city without any garrison nearby, imho).

I would like to know how to force AI to siege a city in order to fight particular battles. I would like to know this also for the eleutheroi because sometimes simply leaving a city with a low public order crashes the game because it tries to give the city to a vanquished faction, instead to rebels.

EDIT: I don't want to use fd and give the city to the enemy, since these are other cases in which my purpose is to fight particular siege battles with particular conditions and particular units for both sides (and also because giving the city with a diplomat spawns enemy units).

The AI will not take a city that they do not want, and it is hard to force them to want a city.

If they are trying to take a different city (your or another AI), they may not try to make any other offensives until they have accomplished that particular goal. Exiting out of RTW and restarting the exe may change the oppinion of priorities of the AI.

You could possibly attack an enemy on your border, but click the withdraw option. Hopefully your army goes into the desired town and the AI's army follows.