You cannot. Since the game is all about expanding faster than your enemies, I'm not sure how helpful it would be if it was possible. I suppose maybe letting someone expand and then making a large capture of what they just put down?
I am thinking more towards the end game. I didn't have a way to make more money, so I wanted to conserve it for a move after the AI took its turn. I guess it could be a pain to implement because if the AI skipped its turn you could end up in a stalemate, unless the game forced all players to take their turn if all players passed the previous turn.