World Cup organisers are hoping a personal message from chief executive Jon Dutton to Australia will persuade wavering NRL clubs and players to throw their weight behind the tournament.
After months of delay caused largely by the latest spike in Covid-19 cases, officials are ready to confirm the tournament will go ahead as planned this autumn and have called a press conference for Thursday morning to make the announcement.
But it is thought several NRL clubs still have concerns over the players' safety in the UK and the prospect of them having to go into quarantine on their return home at the end of November.
Half the 16 nations will be travelling from the southern hemisphere, most of them belonging to NRL clubs.
Last-minute lobbying has included a video message delivered to the NRL in which Dutton said: "I do fully understand the current challenges you face.
"The pandemic has brought nothing but challenges for us all to navigate.
"We will stage the tournament this year as planned. It is imperative that we provide the safety possible environment for players and staff.
"We fully appreciate and respect it will be the players' choice if they get on the plane and come to England. We have undertaken to provide a number of bio-security measures.
"The mandatory 14-day quarantine return home to Australia is the hardest challenge of all."
It is thought World Cup organisers have agreed to foot the bill for charter flights to bring an estimated 400 players and officials from Australia.
Teams will be able to name expanded squads with provisions to draft in players for late withdrawals.
Australia Rugby League chairman Peter V'landys, who took the decision to re-locate all the Sydney-based clubs to Queensland following a rise in infections in New South Wales, has confirmed the commission has yet to give the go-ahead for Australia to compete.
We can't wait for the next international tournament to be hosted in England: Rugby League World Cup 2021! 🏆 Which nations do you think will claim the 3 trophies?#RLWC2021 pic.twitter.com/ROcSvVmOEs — Rugby League World Cup 2021 (@RLWC2021) July 12, 2021
New Zealand RL chief executive Greg Peters says he signed the participation agreement but that it was conditional on receiving guarantees over coronavirus protocols and procedures being put in place, which he has yet to receive.
And Peters warned on Twitter: "World Cup should be best of best or not at all."
World Cup officials, who began planning for the event more than five years ago, pointed to the recent success of Euro 2020 and Wimbledon as evidence that England can host global tournaments safely.
It is thought the Government, which provided £25million in funding, pushed strongly for the tournament to go ahead.
World Cup should be best of best or not at all — Greg Peters (@GPRUGBYCEO) July 13, 2021
Whether the Kangaroos are able to field a full-strength team or not, being able to avoid a postponement will be a major relief to the organisers, who had put in place a host of broadcasting and sponsorship deals and arranged base camps for all 16 teams.
The women's and wheelchair events will run alongside the men's tournament and will take place in 21 venues across 18 host towns and cities.
The World Cup will be the most visible rugby league event in history with all 61 games across the three competitions being broadcast live on the BBC.
A 12-month postponement would have put the tournament up against part of the FIFA World Cup but organisers now have the opportunity to capitalise on the feel-good factor generated by Euro 2020 with the likelihood of full stadia.
