South African rugby will benefit from two of its teams playing in the northern hemisphere PRO14 competition but this will not come at the cost of existing relationships in the south, SA Rugby chief executive Jurie Roux says.

The Cheetahs and Southern Kings will join an expanded PRO14 for the new season after being culled from Super Rugby. They will take on clubs from Ireland, Italy, Scotland and Wales.

Roux said the move into European competition would not change SA Rugby's relationships within SANZAAR, the grouping of Argentine, Australian, New Zealand and South African unions, who run the annual Rugby Championship and Super Rugby competitions.

South Africa's Bulls, Lions, Sharks and Stormers will continue to compete in Super Rugby.

"We are contracted to SANZAAR until the end of 2020 and will be going into a negotiating period again in the next two years," Roux told a news conference in Cape Town.

"We have benefited greatly from the rivalry against Australia and New Zealand and a further relationship is likely to continue to be of great benefit to South African rugby. But joining the PRO14 expands our horizons.

"But to not play in the southern hemisphere competition is unthinkable. We would suffer financial harm."

Roux added that if there is a clash of fixtures, SA Rugby will give priority to the PRO14 over the domestic Currie Cup, where the Cheetahs have started their campaign with three victories.

"We believe participation in PRO14 will bring new intent to our rugby and it introduces summer rugby to our country," Roux said.

Martin Anayi, PRO14 Rugby's chief executive officer, said they had been looking to expand for some time.

Although the chance for the Cheetahs and Kings to join the PRO14 only came up after the teams were dropped from Super Rugby last month, it fitted into previously laid plans, he said.

"This is a ground-breaking feat and a true first in world rugby as we will see north versus south compete on a regular basis," Anayi said.

"We sit now in an economic situation where we have to try and do things differently and we needed to look at bigger rugby markets and spread across multiple territories."