It has also emerged that Ospreys could qualify automatically with Cardiff Blues facing Scarlets instead.

That could happen if Leinster beat Saracens in this season's Champions Cup final on 11 May AND the last four in the second-tier Challenge Cup all qualify through their domestic leagues.

It follows a "clarification" by Pro14 administrators.

Ospreys are due to host Scarlets on Saturday, 18 May (19:45 BST), and that match will go ahead if Saracens beat Leinster in the Champions Cup final.

But it would be delayed until after 25 May - possibly Wednesday, 29 May - if Leinster win.

And it could between Cardiff Blues and Scarlets with Ospreys qualifying automatically if the Pro14 gets an eighth qualifying place as a result of Leinster success.

It boils down to the way the 20th place in the Champions Cup is allocated and the Pro14 being split into two conferences instead of one league table.

The Pro14 has seven places in the Champions' Cup - six for the teams who finish in the top three of its two conferences and a seventh decided by a play-off between the teams which finish fourth.

An eighth would be allocated if Leinster win the Champions Cup and the four Challenge Cup semi-finalists - Clermont Auvergne, La Rochelle, Harlequins and Sale Sharks - clinch top six league positions in their domestic leagues.

All are currently in contention to qualify.

However, the regular English Premiership season does not finish until 18 May and the French Top 14 on 25 May.

Wales may have to wait

Wales' World Cup preparations could be affected by any delay.

The 42-man training squad are due to report for duty four weeks after playing their final matches of the domestic season.

That was due to be 27 May for Dragons and Blues players, and 18 June for Ospreys and Scarlets.

It could now be as late as the end of June with more than half Warren Gatland's training squad made up of Scarlets and Ospreys players.