I'm sorry, right after I posted I've found the answer to my prayers: "synchronize remote"
That seems to be exactly what I need.

Is there a way to perform a single update on the remote folder? I need something like keepuptodate that only executes once. So I can launch the script whenever I need it to update the remote directory with newer files. I've tried different variants of "option confirm" and "option batch" along with "put *" but I haven't been able to find a way to write a script that uploads only newer/modified files only once.
The files that have been removed locally should not be removed from the server, only new/updated files should be uploaded.

Thanks,
Tom