The British Boxing Board of Control (BBBofC) has written to Wales’ First Minister Mark Drakeford to clarify whether Chris Eubank Jr’s middleweight fight with Liam Williams can go ahead.
Cardiff’s Motorpoint Arena is set to stage the bout on Saturday, 5 February.
In a letter seen by BBC Sport Wales, the BBBofC say it will not be viable to hold the event in Wales without fans.
Current restrictions in Wales mean the fight would need to be staged behind closed doors.
Ministers will look at easing Wales’ Covid rules when restrictions are reviewed next week, Mr Drakeford has said.
But he said it was a “big if” whether the situation would allow any change to be made.
Wales’ main sporting events will be held without spectators this weekend.
That is in line with government policy in Wales, with large outdoor meetings prohibited since Boxing Day in the fight against Covid-19.
It appears highly likely sporting events in Wales on the weekend of 22-23 January will also be played behind closed doors.
Swansea City have moved their Championship game with Preston on Saturday, 22 January to a 12:30 GMT kick-off to allow fans to stream the match.
There are currently strict limits on the number of people allowed to meet indoors in Wales, a huge issue for staging boxing, with two-metre social distancing rules applying in public places.
In Wales nightclubs are currently closed, with limits on hospitality businesses, sporting events and who people can meet indoors and outdoors.
Eubank Jr’s middleweight fight with Williams has already been postponed twice, most recently after the BBBofC suspended boxing for the month of January.
It was originally scheduled for 11 December, but was put back to 29 January after Williams suffered a shoulder injury.
In a letter sent to Mr Drakeford, BBBofC general secretary Robert Smith says the event would be important for Welsh boxing, but warns that a venue in England will be sought as a replacement unless clarity is offered on whether a full crowd can attend.
“Throughout the pandemic we have kept regulations under regular review, with our approach being informed by the latest available scientific and medical advice,” a Welsh government spokesperson said in response.
“The cabinet is reviewing the situation on a weekly basis.”
Williams and Eubank Jr, 32, have a bitter rivalry and a win for either man will boost their chances of securing a world title shot in 2022.
The fight moving away from Cardiff would be a blow to Wales’ Williams, 29, who has rarely enjoyed home advantage in the biggest bouts of his career.
It remains possible the fight could be postponed for a third time, allowing sufficient time to sell tickets if restrictions in Wales are relaxed.
The fight with Eubank Jr will be the first for Williams under new trainer Adam Booth, following his decision to split with Dominic Ingle.
