Delete Unwanted Revision

I am trying to remove an unwanted revision. For example: There is revision A.1, A.2 and B.1. I would like to remove B.1.

The options available in Windchill are:

1. Delete all iterations of each object

2. Delete all revisions of each object

3. Delete latest iterations of each object

There doesn't seem to be an option to delete latest revision of each object. I choose #3 and I get an error message saying

"Cannot delete the latest iteration of object(s) 'Publication Source  - test ifp tag template location, B.1' because it is the only remaining iteration for revision"

Does anyone know how I can remove this one revision so that the file reverts back to A.2?