Don't forget that you can force them into peace by having a higher score than them. Build more ships, colonize and destroy some of their ships and colonies.
[This message has been edited by General Hawkwing (edited 29 December 2000).]
A good way to pump up that score is by building bases. A few space-yard bases will not only allow you to increase your navy at a much faster rate but will also give you a nice lift to your score.