The Magners League Round 11 fixture between Ulster and Ospreys, rearranged for Friday 19 March at Ravenhill, has been postponed.
The reason for the postponement is that Ospreys are unable to supply suitably experienced front row players in their match squad as is required under the Magners League rules and IRB rules.
This rule was introduced for health and safety reasons and Celtic Rugby could not sanction a match in these circumstances.
Celtic Rugby recognises the great inconvenience this will have on Ulster Rugby and their supporters, as well as Celtic Rugby's commercial partners, particularly BBC Wales who were due to broadcast the match live.
Until Celtic Rugby has had the opportunity to review the matter there will be no further comment.
Ulster Rugby will advise supporters of the new date as soon as it is released.