World Rugby would back Pro12 expansion to North America
World Rugby would support North American teams joining the Pro12, chief executive Brett Gosper has said.
Pro12 officials have held talks that could lead to US and Canadian sides being involved in the future.
Four teams each from Ireland and Wales plus two each from Scotland and Italy make up the current format, but the possibility of the Six Nations moving has encouraged hopes of expansion.
"We'd be supportive of any competitions including US-based sides," said Gosper.
"The US market is a very important market for rugby. It's a high-growth market, it's the fastest-growing team sport in the USA.
"It certainly will, we think, provide us in the future with huge revenues to World Rugby through our Rugby World Cup product, which all gets invested back into the game around the world.
"That competition, or the Aviva [Premiership], or the Top 14, or Super Rugby - they're all competing for players and competing for eyeballs on broadcasts, so we understand why they would be interested in having a US team in their competition.
"From our point of view, it would be great because it would be developing players in that area who otherwise would have to come to Europe.
"Anything that keeps and inspires some home-grown US players can only be good for the development of that sport."
Pro12 managing director Martin Anayi has underlined the desire for North American teams to be included, with Houston and Vancouver earmarked as possible host cities.
He wants the annual Six Nations tournament involving England, Ireland, Scotland, France, Wales and Italy to be moved in the calendar and expects World Rugby to help that happen.
However, Anayi accepts that a long-talked-about global season has to be implemented for any Pro12 revamp to take place, and Gosper suggests it is a delicate issue.
"At the end of the day, the global calendar is a negotiation of what's in the common good for as many of the competitions, clubs and nations as possible," said the World Rugby chief.
"It's not an easy thing to reconcile and movement somewhere creates issues somewhere else.
"All I can say at this point of time is we would support their ambition to include an American side in the [Pro12] competition.
"We'd have to look at, with the other stakeholders, what that would mean in terms of calendar shuffle or change."