The inaugural 'Rugby X' tournament will feature a host of Olympic medallists after England, Ireland, USA and France all signed up for the international five-a-side event at London's 02 Arena.
The four countries will all enter men and women's teams on 29 October, with Argentina entering just a men's side.
Tournament organisers are talking to the Barbarians about taking the sixth spot in the men's competition.
There will be four teams in the women's event.
All athletes across the men's and women's competition will be paid the same fee for taking part.
Tom Mitchell, Dan Norton, Ollie Lindsay-Hague and Phil Burgess are among the Team GB Sevens silver medallists from the 2016 Olympics who are set to feature for the England men's side, with Amy Wilson-Hardy and Holly Aitchison among the women players likely to be involved.
It's understood the Barbarians - if confirmed - will include a number of Fiji's Rio 2016 gold medal winners, while some big 15-a-side names could also be included if not still playing at the World Cup.
The event will be split into two sessions, an afternoon slot aimed at families, and an evening one targeting 18-34 year-old event-goers.
It is hoped the inclusion of established Sevens players will help give the fledging concept credibility, as Rugby X tries to revolutionise the sport at both elite and grassroots levels.
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