Fiji is set to be included in an eight-team tournament alongside the Six Nations team to replace the Autumn Tests.
Japan will also be in the mix which will begin on November 14, two weeks after the final round of the 2020 Six Nations is completed
Wales’ game with Scotland, Ireland’s trip to France, and England’s match in Italy have been scheduled for 31 October after being postponed in March.
The other outstanding tie – Ireland v Italy – will be played the week before.
Scotland’s meeting with Wales appears more likely to be held at Twickenham than in Cardiff.
No decision has been taken yet on whether fans will be allowed into the Six Nations matches, but the RFU is hopeful supporters will be able to attend games in the new tournament.
RFU chief executive Bill Sweeney said last month the union is planning for up to 40,000 fans to be able to attend the Twickenham Tests, pending government approval.
England will face Wales, Ireland and Fiji in one group, with the latter two fixtures at Twickenham and the venue of the first game still to be decided.
In the other pool, Scotland will host Japan and France at Murrayfield and face Italy in Rome.
The tournament will be staged on four consecutive weekends until 5 December, with each team facing their equivalent in the other pool on the final weekend, with the venue to be decided.
Official confirmation of the schedule and the venues is expected in August.
It means Gregor Townsend’s side’s Autumn internationals against Argentina and New Zealand have been cancelled, while the one against Japan could be moved.