The competition will be played in the existing July and November Test windows in alternate years, outside of British & Irish Lions tours and the World Cup, the two organisations said in a statement.

It will feature the four Rugby Championship teams -- Argentina, Australia, New Zealand and South Africa -- and the Six Nations sides of England, France, Ireland, Italy, Scotland and Wales.

Two spaces have also been reserved for invited unions to join the SANZAAR teams in the so-called "World League", potentially Japan and Fiji.

A second-tier competition will be also established by governing body World Rugby featuring sides from Europe and the rest of the world, paving the way for promotion and relegation.

Creating the new concept was a "testament to the strong ambition across all parties, motivated by delivering context and a stronger narrative around the July and November windows, that can excite players and bring new fans to the game", SANZAAR and the Six Nations said.

"The impact this will have on the game will be to drive its growth and long-term sustainability," they added.

"Establishing the two competitions will pave the way for promotion and relegation matches, contributing towards a valuable pathway for teams, and will support ambitions to sustain and grow the global game."

Leagues, major stakeholders and players had all been consulted which the organisations said had been key to ensuring player welfare was "a fundamental priority in all decision making".

Although no format has been confirmed, reports suggested teams from the north would travel south for three tests in July and then host three more games in November.

The tournament, expected to see two groups of six and a grand final, would be in addition to the Six Nations and Rugby Championship, which are set to retain their spots on the calendar.

Traditionally, the July Test window has been used for bilateral Test series, while southern hemisphere teams often travel to Europe to take on their northern rivals in November.