update twitter only when a post is published

Hi,

is there a setting for updating twitter only when a post is published?
I mean, do not update, when a post is edited.
I receive some posts with syndication. Sometimes a feed is updating (reason unknown), the complete feed is twittered again.

greetings
Jens

http://wordpress.org/plugins/wp-twitter/