Pro14 organisers have confirmed they are in talks about increasing the number of South African teams in the competition.
Cheetahs and Southern Kings have been the two sides involved in the Pro14.
Kings will not be involved in 2020-21 after going into liquidation and negotiations are ongoing about which franchise will take their place.
A Pro14 statement said: "On August 25, Pro14 Rugby acknowledged under current international travel restrictions it is not possible for South African teams to fulfil Guinness Pro14 fixtures until 2021.
"Pro14 Rugby welcomes the news that the South African Rugby Union (SA Rugby) has been able to arrange a domestic schedule for its professional teams and that this is the first step in the return of their teams to on-field action.
"SA Rugby's long-standing commitments are to field two teams in the Guinness Pro14 and in light of the withdrawal of the Southern Kings, discussions are on-going about fulfilling this agreement from 2021 using a replacement team from its current professional franchises.
"Additionally, both Pro14 Rugby and SA Rugby are in early discussions about potentially expanding the tournament and deepening our partnership to include more South African franchises from 2021."
The league confirmed in August the South African sides will not play in the Pro14 for the rest of 2020, missing the start of the 2020-21 season, but Pro14 bosses are still negotiating with SA Rugby about involvement in this campaign.
The 12 teams from Wales, Ireland, Scotland and Italy will begin the new campaign with the first round of 11 fixtures not involving the South African sides.