The Daily Post said this was announced by the MSG chair, the Solomon Islands prime minister Manasseh Sogavare, in Port Vila at a meeting with West Papuan representatives.
Mr Sogavare reportedly said Solomon Islands, Vanuatu and New Caledonia's FLNKS movement would admit West Papua at the next MSG Leaders Summit in Vanuatu even if Papua New Guinea and Fiji stay away.
An MSG summit planned for last week was cancelled without a reason being given after it had already been deferred earlier in the year.
The United Liberation Movement for West Papua has been seeking to become a full member of the MSG which last year made Indonesia as an associate member.
The Chairman of the Vanuatu Free West Papua Association Pastor Allan Nafuki said if Fiji and Papua New Guinea do not turn up for the next summit, the three other members will have no alternative but to go ahead and vote West Papua into full MSG membership.
Concern about human rights abuses by Indonesian forces in West Papua was raised by several Pacific Islands countries at the United Nations last month, triggering a rebuke from Jakarta for alleged interference in Indonesia's domestic affairs.