How to cut installed ceramic tile to transition with wood floor?

We are getting ready to have hardwood floors installed and there are two doors where the wood will transition to existing tile. One transition is to a bathroom and the other to a pantry. Unfortunately the tile is 12" square and lies dead center in the doorway where the transition occurs. I need to split/cut the tiles in the doorway so the transition molding can be placed directly under the door when its closed. Any ideas?