Premiership chief executive does not like the idea of international breakaway
Premiership Rugby bosses have warned against a "nonsense" breakaway of individual nations from the global Test calendar.
Aviva Premiership chief executive Mark McCafferty has challenged top administrators to thrash out a new long-term deal to solve the "unsustainable" international season.
The existing international fixture agreements expire after the 2019 World Cup in Japan, with New Zealand hinting they would refuse a renewal under the status quo.
McCafferty believes any effort by a top nation to go it alone in building fixtures schedules could seriously damage rugby's professional-era progress.
"If we think four to eight years ahead, for countries like the USA and Japan not to have a regular profile of fixtures in the international calendar is just a nonsense," said McCafferty.
"Those countries have got to be brought into that. And from the club game's point of view, we have to separate the club and international calendar."
Guinness PRO12 chiefs have mooted delaying the start of the RBS 6 Nations by six weeks with club seasons being completed in advance - but McCafferty insisted Premiership Rugby do not consider that a solution.
A long-mooted play-off between European and Super Rugby champions remains on the agenda for Premiership Rugby, but the English clubs' governing body staunchly opposes a move to summer fixtures.
McCafferty believes crisis talks featuring all the major players from rugby's global powers will take place before the end of the year, with a view to resolving this latest impasse as soon as possible.
"A lot of bilateral and trilateral discussions are going on in an unstructured way," said McCafferty. "I think that will happen before Christmas.
"There are some practical difficulties in doing that, but it's one of the most important issues for the game and there's not much time left.
"We're not going to summer rugby, neither is the southern hemisphere from their perspective, it's more about trying to dovetail the seasons a bit better.
"A world club play-off would be a nice thing to have at some point. We've long been a proponent of a world club championship but we've got to find space in the calendar to do it."
Rejecting the idea of moving the Six Nations, McCafferty said: "We don't like that particular idea, but we do have some of our own ideas and concepts.
"But we think that the best thing to do is to get all the main stakeholders in one building at one time and to work through it. Because we've got some fairly strong views ourselves about separating the club and the international calendar more.
"That's the next part of our development, to try to get a greater distinction there between the international and the club game.
"That's one concept, but we've also got to listen to others.
"I think the international season structure is unsustainable as it is at the moment.
"It's coming to a head for sure. We're talking about what happens after the World Cup in Japan in 2019, so we've got to focus a few years out.
"But I don't think you can really make any progress by just lobbing out individual ideas there, without getting in a room and trying to work through it."
While the Celtic and Italian PRO12 league have already confirmed they will explore the potential to add a franchise in the USA, Premiership Rugby will not.
McCafferty insisted the Premiership will not expand its teams beyond England, but also reconfirmed plans to stage another league fixture in the US in the coming campaign.
"I don't see that in the foreseeable future," said McCafferty, when asked if the Premiership would consider creating a team in the USA.
"We are an English league, that's where our strength is. We've certainly no plans to change.
"We'll look to grow profile in the States for sure, and we've made a couple of big breakthroughs on that last season.
"It's about gaining profile for the Premiership competition in the States rather than basing any teams there.
"We're just putting together some last-minute details on our fixture in the US for the season. It will be a few weeks before we're able to confirm everything, but it will happen."