Group Chief Executive David Moffett told the WRU website that after a "very full and frank" meeting, the executive board agreed to support the move triggered by Blues chairman Peter Thomas and supported by Warriors money-man Leighton Samuel.
"The board has decided they will not stand in the way of a potential merger," Moffett said. "They recognise it is only early days yet, and there's a long way to go before such a merger comes to fruition.
"The WRU will act only in an advisory capacity and will not be pushing any of the regions to merge. Having said that, we still believe that four regions are the right number - from a playing strength point of view and as far as the financial implications go."
The proposal now meets its toughest obstacle - the shareholders of Cardiff RFC, many of whom vehemently oppose the idea. Warriors fans - who are still coming to grips with last year's merger of Pontypridd and Bridgend - are also angry at the proposal.