Cape Town - Australia and South Africa would lose one team each under a potential new streamlined 16-team Super Rugby model under consideration, a report said on Friday.
The southern hemisphere-based tournament was only expanded this year to 18 teams with the addition of new sides from Argentina, Japan and South Africa.
But the report said new models were already being investigated, with one option being to drop two teams, one each from Australia and South Africa.
Another proposal would see South Africa losing two teams while yet another model involves expanding the tournament, as officials tinker with ways to improve the geographically stretched competition.
The review for governing body SANZAAR, which is being conducted by consultants Accenture, is still some months from settling on a preferred structure, Fairfax Media said.
It said Accenture have completed a consultation process with 28 stakeholders, including the 18 current teams, the national unions from Australia, New Zealand, South Africa, Argentina and Japan, plus the host broadcaster from each country.
"Sources close to the discussions stressed that a number of different models were being discussed," the newspaper said.
"But Fairfax Media understands the Australian Rugby Union board spent time at its meeting last week discussing the possibility that the preferred structure would require Australia to surrender one of its Super Rugby licences in time for the 2018 season."
Fairfax Media said the SANZAAR board, which comprises the chief executives and chairmen of the joint venture partners Australia, New Zealand, South Africa and Argentina, hopes to see a recommended model over the coming months, with a final structure and timeline agreed by the end of this year.
"Such a model... would return the tournament to a more workable 16-team, four-conference format," it said.
Fairfax Media said the Perth-based Western Force or the Melbourne Rebels would most likely be in the firing line as the Australian franchise to be dumped.
ARU CEO Bill Pulver said everything was open for discussion, but it was unlikely changes would be made until the end of the 2020 television broadcast deal.
"Everything is on the table," Pulver told reporters in Sydney on Friday.
"The broadcast agreement is from 2016-20, so that's the most likely time we're looking at."
A SANZAAR spokesperson told AFP: "It's all speculation at present. We are in middle of the SANZAAR strategic plan review process with Accenture.
"As publicly stated the 10-year review is looking at all options in terms of tournament formats, commercial opportunities and governance."