How to convey displeasure to another race

In my current game, there is another race that has parked a troop transport near my world, watching and waiting a presume. Anyway, the current relationship I have with them neutral. But how do I convey to them to move along? I would do same to them they would be able to tell me that they see me doing this and do not like it (based upon what I have read).

Anyway, thanks