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.
"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."