Yes, you can do this on the Request a UID Page.
The table on this page lists people for whom UIDs have been requested. If a UID has not been generated for a particular individual, users may use the Cancel Request Button in the right-most column of that person’s row. If the UID has already been generated, users can purge it from the system by clicking on the Purge UID button in the right-most column of that person’s row.