RFL boss Ralph Rimmer says October's Ashes series between England and Australia will be hard to deliver.
England were due to host Australia in October for a three-Test series but with the NRL's revised season, that looks highly unlikely to happen.
Speaking on the Rugby League Show, Rimmer did not go as far as to say it has been ruled out, but said that sacrifices had to be made.
"If I am being honest it is going to be tough," said Rimmer.
"We are speaking to the NRL on a regular basis. We have not quite come to a conclusion yet, but I think we all have to accept in very difficult times, some sacrifices have to be made.
"That conclusion has not quite been finalised but hopefully I will have something to announce in the very near future. The series is important to us and to the Australians, nevertheless we do have to be realistic and it is under some threat.
"We are still trying to find a solution but it is going to be a tough call. We shall see how we go and we will have to do something with England at the end of the year whatever happens as we are preparing for the World Cup in 2021.
"At this moment we have plan B to plan Z - game time would be preferable but it not then certainly some time in camp together. The Super League clubs are very supportive of England's push for the World Cup so I know they will help us."
Rimmer also commented on the likelihood of promotion and relegation to and from Super League in 2020.
"There has been plenty of discussions as you can imagine as there are plenty of interested parties," added Rimmer.
"Everybody puts a very coherent argument together - both Super League and the Championship. We understand the stresses and strains it puts on people and the implications of either keeping it or not keeping it.
"Ultimately it is a RFL board decision and they will make that decision in the best interest of the game.
"These are imperfect times and the health of the nation is at stake - that has to come first. We will find a way out of this and emerge in our 125th year very strong and be very proud of our sport again."