How can I stop a calendar sync?

I made the mistake of deleting some unwanted manually calendars from an iPhone which had misleading names. I noticed that the content was not what the name suggested when I opened them on the Mac but by that time iTunes had already started with the sync.

Although these calendars have now been removed from the list to sync, there is still a message at the end of each sync asking for confirmation to delete hundreds of entries. The only options on the dialog are to proceed with deleting or sync later (or to show details which confirm they are entries I don't want to delete).

Is there a way to get iTunes to skip the deletions and forget about them the next time? I want to leave the calendars and all their entries on the Mac.

I've noticed there is a folder in ~/Library/Calendars/ called "Calendar Sync Changes" which contains a large number of .tmp files. Each appears to be a plist containing references to deleted/modified events and calendars. Would removing these files be sufficient or are they referenced by iTunes using something more than the folder name?

Looking through the Calendars folder I've found a lot of old data which I did not expect to see so it is possible these tmp files are relics and the information on the pending sync is now in iTunes.

I do not use iCloud or any third party cloud syncing solution. Everything is done locally.