Officials from Wales' four regional sides remain hopeful of a resolution to the row, which has led to the cancellation of the Celtic League in 2005-2006.
The Welsh Rugby Union believe clubs can play in an Anglo-Welsh Cup in addition to competing against their Scottish and Irish opponents.
However, the Scottish and Irish Unions are upset at the scheduling of fixtures, which could affect teams in the Heineken Cup, Europe's top competition.
Cardiff Blues chairman Peter Thomas said: "We believe the proposed fixture list can accommodate the aims of our Celtic League partners along with the desires of the fans, players and broadcasters."
Llanelli Scarlets, Newport Gwent Dragons and Neath-Swansea Ospreys also support the WRU following their agreement with the Rugby Football Union to compete in the Anglo-Welsh Cup.
As a result, Ireland and Scotland plan to play in their own competition next season at the expense of the Celtic League.
However, Scarlets chief executive Stuart Gallagher insists the proposals do not mean Welsh sides are not committed to the Celtic League.
He said: "We are prepared to commit to the Celtic League for the long term - we believe the Celtic League fixture list is exciting and challenging."
The revenues offered by playing English clubs are thought to have made the risk worthwhile for the WRU.
