The southern hemisphere tournament currently includes five teams each from South Africa, New Zealand and Australia.
The SANZAR executive committee agreed on a "preferred model" during a meeting in Sydney on Thursday, it said in a statement.
"Today's meeting was another important step in deciding the future of Super Rugby," SANZAR chief executive Greg Peters said.
"Encouraging progress was made and we now have a preferred model that involves six teams from South Africa and a new team from Argentina.
"The model will now be taken to the National Unions for approval before SANZAR presents its final position to broadcasters and fans in due course."
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- Super Rugby