The Lions, who finished 12th, will play in the Challenge Cup, while the Cheetahs, who have not played in the URC, have been invited into the event.

Organisers say their inclusion with bring "a new level of elite rugby".

"This is a crucial step forward in bringing to life our vision of growing the game and our own tournaments, continuing to deliver strong returns for our leagues and creating an ever-higher standard of mouth-watering matches for our fans," said European Professional Club Rugby (EPCR) chairman Dominic McKay.

The EPCR says the arrangement will cover next season "and beyond".

The Sharks, Stormers, Bulls and Lions' eligibility for European competition was confirmed when they took places alongside Irish, Welsh, Scottish and Italian teams in the rebranded URC last year.

The quartet replaced the Kings and Cheetahs, who had been the South African participants in the Pro14 - the tournament's previous incarnation.

The South African Rugby Union (SARU) is attempting to align more closely with Europe, with which the country shares a time zone, rather than the southern-hemisphere powerbase of New Zealand, Australia and Argentina.

South Africa's club sides moved away from playing in Super Rugby against teams from New Zealand, Australia and the Pacific Islands in 2020.

At international level, the Springboks have committed to the Rugby Championship, but are reported to be exploring the possibility of joining the Six Nations.

"We now have an opportunity to also start rubbing shoulders with the top clubs from England and France in two other competitions that have caught the imagination of rugby supporters around the globe for more than two decades," said SARU chief Jurie Roux.