World champions South Africa are set to remain in the Rugby Championship until at least 2030 despite the suggestion they could join the Six Nations.
Speculation around the future of the Springboks in the international tournament has increased in recent months.
Holders South Africa withdrew from this year's Rugby Championship amid complications linked to the coronavirus pandemic, leaving Australia, New Zealand and Argentina to play a three-team tournament.
This followed South Africa's vote to withdraw domestic clubs from Super Rugby and begin talks over a move to Europe's Pro14.
But SANZAAR, which organises both the Rugby Championship and Super Rugby, said on Wednesday all four of its nations - including South Africa - had "committed to an international rugby future through to 2030".
The Rugby Championship will change from a six-match to 12-match structure, allowing all four teams to play each other home and away through the new mini-tour match schedule.
The move would appear to end any imminent Springboks move to link up with England, Ireland, Wales, Scotland, France and Italy.
SA Rugby chief executive Jurie Roux said: "We welcome the changes announced to the Rugby Championship with our SANZAAR partners and we are looking forward to seeing what the new strategic plan for the competition entails, with possible international expansion on the cards.
"Although we had to change our domestic focus, we still have a long history with the All Blacks and Wallabies as well as a long-standing friendship with the Pumas and we look forward to more world class Test rugby.
"Ever since the Tri-Nations was first contested in 1996, and more recently the Rugby Championship from 2012, a team from the Southern Hemisphere has won the Rugby World Cup five out of six times - which is testimony to the high quality of Test rugby played on this side of the equator."