rsync using sudo via remote shell

[Achim Stäbler]

Hi!

I'd like to use rsync to make incremental backups of my webserver. The 
ssh daemon on the server does not accept root logins, but I can login 
(key, no password) as a regular user and then execute rsync via sudo.
Without root login limitations I'd be able to use something like

rsync -avz -e "ssh -i /home/backup/.ssh/id_dsa" backup at server:/ 
/backup/server/

Unfortunately I can't figure out how to tell rsync to execute its remote 
instance via sudo. Any help appreciated.

Thanks,

Achim.