Wales's four regions will have showdown talks with the Welsh Rugby Union next week, ready to take legal action for the right to play in cross-border tournaments without needing permission from their governing body.

The regions are angry that the WRU used last month's international programme to try to persuade players who are coming out of contract with the regions at the end of the season, including Sam Warburton, Leigh Halfpenny and Alun Wyn Jones, not to sign new deals.

The participation agreement between the regions and the WRU, which covers the release of players to Wales, runs out at the end of the season. The union has given the four until the end of the month to commit to what would be a rolling on of the agreement until 2018 with no extra money.

The players were told that if the regions did not sign an agreement which would mean that they would receive the same amount in real terms in 2018 as they did in 2009, the union would offer them central contracts and look to set up their own teams.

The regions and the WRU will meet on Wednesday when the professional rugby game board convenes for the final time before the 31 December participation agreement deadline. One reason that the four have refused to sign is uncertainty over the future of the Heineken Cup and the offers that have been made to players in the last year of their deals are conditional on there being a European tournament next season.

The regions pledged their support for the Rugby Champions Cup, a tournament proposed by the England and French clubs to replace the Heineken Cup, only for the WRU to commit them to the competition run by European Rugby Cup Ltd at a meeting of unions in Dublin towards the end of last month.

The regions have taken legal advice and believe a precedent set 20 years ago makes success against the WRU more likely than not. Newport County, the football club which had been reformed after going bankrupt, was told by the Football Association of Wales that it would no longer be able to play in the English league system and had to take part in what was the then League of Wales. The club took the FAW to the high court and won, and last season secured promotion back to the Football League.

"The WRU, by telling us we have to play in the Heineken Cup with a more modest increase in funding than the other teams in the tournament at a time when we receive less centrally than any of them, are not allowing us to run our business properly," said one regional official. "It amounts to a restraint of trade. We believe we have the right to explore opportunities elsewhere, whether it is an Anglo-Welsh league or an alternative to the Heineken Cup. We are being squeezed by our own union to the point where they are telling our players not to sign contracts. This cannot go on."

The regions are considering calling an extraordinary general meeting of the Welsh Rugby Union and proposing a vote of no confidence in the executive, not because they entertain any prospect of winning but because there is a desire to make their dealings with the union in the last couple of years public.

Some players have already decided not to get involved in the crossfire. The second-row Ian Evans is leaving Ospreys for Toulon and the region has given permission to the Wales hooker Richard Hibbard, who has another season on his contract, to talk to Wasps and will not demand a transfer fee if the forward agrees terms out of respect for the 10 years he has spent with the side. Contract offers to his fellow Lions Alun Wyn Jones and Adam Jones remain on the table.

Scarlets hope to retain the fly-half Rhys Priestland, a target for Gloucester, and the centre Scott Williams, but the lack of progress on Europe has made the four regions, who have agreed to stick together and speak as one, determined to go their own way if talks with the WRU next week yield nothing.