Passing through wormholes with other ships

Does anyone know if there's any way to pass through a wormhole that another race's ship is occupying without initiating combat? I had good relations with the Amonkrie (sp?) but then they parked a small ship in one of my home systems wormholes and just sat there. I eventually had to go in and destroy it just to leave my own system. Later I moved a colony ship through an unexplored wormhole and got attacked by a small fleet of their frigates. Now, of course, I can't just let the senseless slaughter of thousands of innocent colonists go unanswered, so I think I'll go and wipe out their entire race, raze their cities to the ground, salt the earth, and basically consign them to the ash heap of history.
Fun Game!