What are ways to provoke AI to break peace treaties/cease fire?

I want to create scenario where player can't directly attack his enemy due to the Senate. In this case player can choose to provoke AI to break peace treaty/cease fire.
But I wonder about ways it can be done.

Ways I know:

* By causing incident with spies
* By asking them to withdraw troops(when there are troops)

Incident with spies causes your government to fall. The best way is to keep asking them to withdraw troops even when there are no troops to remove. They dislike you more and more every time you ask and eventually declare war.
The other way is to set a trap for them. Create a defenseless small city near their land. They are likely to walk in and take it. Of course this way you lose a prime tech to them so this is not always worth it.

One way is to ask a third party to declare war on your enemy. It costs gold, but your enemy will "discover your betrayal" and declare war and you won't even have a damaged reputation. I don't know if your enemy will always declare war, however.

On the subject of a trap, often, you can just leave a caravan in their territory, maybe hiding a diplomat under it.