Wales' regional sides have backed the Welsh Rugby Union in their Celtic League row with Ireland and Scotland. The Ospreys, Scarlets, Dragons and Blues will support the WRU in pushing for an Anglo-Welsh Cup in 2005/6.
Plans for the new event so angered Irish and Scottish clubs they pulled out of the Celtic League in protest.
"We're committed to the Celtic League, but by adding the cup we believe we're delivering the fixtures people want," said Scarlets chief Stuart Gallacher.
"Their [the Irish and Scots] decision could spell the death knell for professional rugby in the three Celtic countries."
Gallacher's stance was backed by Cardiff Blues chief executive Robert Norster, who added:
"We will try to be conciliatory to our Celtic League partners, we want the tournament to continue."
WRU officials say they are still hopeful the league will go ahead and say they will make concessions over fixtures to try and reach a compromise.
One of the major bones of contention which angered Ireland and Scotland was that the Anglo-Welsh Cup - which would effectively replace the Powergen Cup - would be played over five weekends in the run-up to Heineken Cup dates.
They feel that would impact on the competitiveness of their teams in Europe's flagship tournament.
The Welsh hope to negotiate these dates and have drawn up a new, proposed fixture list, but this would need co-operation from broadcasters and England's Zurich Premiership sides as well as the go-ahead of Scotland and Ireland.
The Irish and Scots remain irate at Anglo-Welsh Cup plans, and would prefer Wales to give their backing to continued talks with Italy and South Africa over a new Rainbow Cup tournament.
WRU chairman David Pickering insists the new proposals will enhance the Celtic League and that officials are keen to be "conciliatory towards our partners."
"We firmly believe this proposal for a Celtic League fixture list services the needs and desires of all the players, coaches, fans, sponsors, administrators and broadcasters within Wales, Ireland and Scotland.
"It delivers a highly competitive and attractive league tournament that would be an improvement on last year's Celtic League because it would be the sole means of qualification to the Heineken Cup for all parties.
"It's obvious to us that our proposed Celtic League structure is a far superior competition to any alternative."
Premier Rugby, the organisation which represents England's top-flight clubs, said in a statement that "the Anglo-Welsh tournament was borne out of a desire to renew traditional rivalries."
It added: "Premier Rugby is shocked and disappointed at reports that the Welsh regions may be expelled from the Celtic League.
"Premier Rugby has always been supportive of a strong and vibrant Celtic League and we feel this would be very difficult to achieve without the presence of the Welsh Regions."