The Six Nations could be played as a home-and-away tournament next season if the Covid-19 pandemic prevents the autumn internationals going ahead as planned.

RFU chief executive Bill Sweeney remains optimistic it will still be possible for England to play planned Tests against New Zealand, Tonga, Australia and Argentina in November, but said several contingency plans were under discussion, including an expansion of the Six Nations to fill the void.

"The preference from both the north and the south is that the original programme will go ahead," Sweeney said. "But of course that's driven a lot by international travel restrictions so both (the north and south) are developing back-up contingency plans.

"There are two or three different options we could go ahead with that feature more northern hemisphere competition around that autumn window.

"One of them if you'd play a Six Nations tournament in that autumn that would combine with fixtures next year and for the first time ever you'd have home and away. It's possible. Every (plan) has pros and cons to it and those are being evaluated."

Plans are already in place for the remaining fixtures of the 2020 Six Nations, suspended amid the pandemic, to be played later this year.

Sweeney said it was too soon to say with any certainty whether international rugby would return behind closed doors, with the RFU looking at several possibilities, including looking at how Twickenham could host games with social distancing in place.

"You would be surprised the impact (a two-metre social distancing) rule has in an 82,000-seater stadium but one metre has a very different impact," he said. "We've run every model so we've got a sense of what that does."