Welsh Rugby Union (WRU) chief David Moffett today sent an ultimatum to the Football Association of Wales (FAW) as the row over unpaid fees for the use of the Millennium Stadium stepped up a notch.
The WRU have revealed that the FAW owes them at least £250,000 for using the arena for matches dating as far back as the 4-0 win against Scotland in February in 2004.
The stark warning means the FAW must "Pay up - or else".
There is even the possibility now that Wales' World Cup Qualifier against England on September 3 could be played elsewhere if the WRU refuse to allow the national side to play at the Millennium Stadium.
Moffett said: "We have been patient with the FAW, who for some inexplicable reason do not seem able to resolve this matter.
"Well, now we hope it is time that sanity prevailed.
"Blocking the England game from being played at the stadium would be absolutely the last resort and it's not the way we want to do business.
"But the fact is we have given the FAW everything they wanted when using the venue and we now expect payment.
"I don't know who's running the show for them these days, but I would say to whoever it is that this is not a trivial amount.
"That's why they were sent the letter, we had no other choice.
"If they are not going to pay it I presume they will come up with a reason - but I cannot imagine what that reason could possibly be."
Alternative venues for the games, should they be required could only be Cardiff City's Ninian Park ground, or the newly built New Stadium in Swansea - both boasting capacities of roughly 20,000 compared to 72,500 at the Millennium Stadium.