Peter Wheeler, one of English rugby's most senior figures, has warned achieving an agreement between rival broadcasters designed to avoid a damaging split in the European club game will be "difficult and delicate".
Premiership Rugby, whose clubs have said they will not compete in ERC tournaments from next season, are adamant their agreement with BT Sport allows the broadcaster to screen European, as well as domestic, club matches.
But ERC have been equally strident in saying their satellite broadcast partner, Sky, retains European television rights.
According to a report in Friday's Daily Telegraph, RFU chief executive Ian Ritchie, a former UK television insider, has been trying to broker a compromise deal between BT and Sky.
Wheeler said he'd been encouraged by the progress made regarding the future of the European Cup during a Six Nations meeting in Paris on Wednesday.
But the former England hooker, who has been closely involved in the talks over the future of European club rugby in his triple role as executive director of English champions Leicester, a Premiership board representative and an ERC director, said resolving the issue of broadcast rights was now the biggest stumbling block to an agreement.
"It seems to be clear that the largest problem is the fact that there are two TV deals, both of which cannot progress under the same terms that were envisaged," Wheeler said Friday.
"I was encouraged by what came out of the meetings this week," said Wheeler.
"Most of the other areas appear to be resolved, so this (broadcast) one is huge.
"And it is a very difficult and delicate issue as well," the 65-year-old Wheeler, a member of England's 1980 Grand Slam team, added.
Premiership Rugby want the Six Nations committee to oversee the European Cup next season. It is a position both French and Welsh clubs have said they would accept.
But even if there is agreement on that point, that still leaves the thorny issue of television contracts.
"If there is a willingness of these parties (BT and Sky) to look at that then there could be progress," Wheeler said.
"But I am sure both feel they have secured exclusive rights already, and so it would have to surround packages that both parties could see equal value in.
"There will still be a number of pretty fundamental issues still at stake.
"From the clubs' perspective we're trying to sell season tickets, and obviously to do that we need to know what competitions we are selling.
"There is a widespread willingness to find a resolution, and so that's what everyone is working towards.
And with next season culminating in the 2015 Rugby World Cup in England, Wheeler added: "Deadlines are difficult to set, but there is one that cannot be ignored, and that is the start of next season."