How can rsync with ssh be used on a non standard ssh port

[eculp at casasponti.net]

I need to use rsync for backup to another machine using a nonstandard  
port for ssh. 722.

For example, when I test using my translation of the man pages:

rsync [OPTION...] SRC... rsync://[USER@]HOST[:PORT]/DEST

I use:

rsync -avz /almacen/testDir rsync://backkup.net:722/backup/

the error generated is:

rsync: server sent "SSH-2.0-OpenSSH_5.1p1 FreeBSD-20080901" rather  
than greeting
rsync error: error starting client-server protocol (code 5) at  
main.c(1504) [sender=3.0.4]

I've tried many variants but none have worked.  Any suggestions would  
be greatly appreciated.

Thanks,

ed