I agree with low. The only way to turn off tho mobilization is to actually sign a peace treaty. You need to do what you must to get another civ to agree to peace (even if it means a sneak attack). If you can't reload a save w/o the mobilization, you can attack someone's worker (that's pretty low on the transgressions list), wait a couple turns, then offer a peace treaty.
Then to butter them up a little, send the worker to your capitol, and offer it back to the civ as a present.