The announcement, made on behalf of the regions by their umbrella organisation Regional Rugby Wales, comes on the eve of summit talks in Dublin aimed at thrashing out a new tournament agreement for the Heineken Cup and Amlin Challenge Cup competitions next season.
Top English and French clubs have no intention of being involved in those discussions, though, forging ahead instead with plans for the Rugby Champions Cup that they initially announced last month.
The clubs, via Premiership Rugby and Ligue Nationale de Rugby, are currently serving a two-year notice period to quit European Rugby Cup-run competitions, which will be completed next summer.
In a statement, RRW said: “Regional Rugby Wales, on behalf of the four Welsh regions, confirms its full support for the proposed new Rugby Champions Cup competitions.
“Whilst there remain elements of detail to be confirmed, it is now clear that there are a number of significant advantages to the new competitions in equality of governance, format, qualification and distribution across the individual participating clubs.
“Consequently, RRW looks forward to working with the WRU (Welsh Rugby Union) to support their efforts and positive engagement in striving to ensure our teams are involved in strong, valuable European clubs competitions in time for next season.”
RRW represents Cardiff Blues, the Ospreys, Scarlets and Newport Gwent Dragons.
RRW’s announcement is a huge development for the Anglo-French alliance following their decision to quit ERC over what they see as an unfair qualification process for the Heineken Cup, notably via the RaboDirect PRO12, and an uneven distribution of funds.
The Rugby Champions Cup is a proposed 20-team tournament run by clubs, rather than unions.
And both Premiership Rugby and LNR, in establishing the Rugby Champions Cup, issued an open invitation to teams from Wales, Ireland, Scotland and Italy to join them.
The WRU, Scottish Rugby Union and Irish Rugby Union have said their clubs will not take part in any European competition unless it has International Rugby Board backing.
The French Rugby Federation is against the Rugby Champions Cup, meanwhile, although the Rugby Football Union has yet to make its position public.
But the Welsh regions, whose financial struggles are well chronicled, have now nailed their colours firmly to the mast.
And while the Anglo-French clubs will rejoice at developments, a strong response from the WRU to RRW can be expected.