This year's Rugby League World Cup in England has been postponed until 2022 after the withdrawal of champions Australia, and New Zealand.
The two countries pulled out of the tournament citing "player welfare and safety concerns" related to Covid-19.
The World Cup, featuring men's, women's and wheelchair events, was set to start in Newcastle on 23 October.
"It became unfeasible and irresponsible for us to carry on," said Jon Dutton, chief executive of the tournament.
"I think it will take some time for international rugby league to recover from this. I hope we can be a beacon of light.
"Certainly we've prioritised player voice and player choice, we know the players want to play, we took our responsibilities very seriously, and we are determined to stage the biggest and best ever rugby league World Cup.
"It's a real shame that it cannot be this year but leadership is about making tough decisions, it's about being responsible, and we've done this in the best interests of not just the tournament but of the sport of rugby league."
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Organisers were given only four minutes' notice that the antipodean neighbours intended to pull out on 22 July, with Rugby Football League (RFL) chairman Simon Johnson calling it a "selfish, parochial and cowardly decision".
Dutton last week gave it a "50-50" chance of going ahead as scheduled this year after discussions with the board and numerous stakeholders, including players.
"There's been some really disappointing behaviour," added Dutton when asked about whether Australia, New Zealand and the NRL had called the shots.
"We can't end up in this position again and we'll make sure we don't."
Delaying the World Cup by a year could mean it clashes with the football equivalent in 2022, but Dutton said a window will be found to avoid such a scenario.
"I am disappointed that we've needed to take the decision to delay the Rugby League World Cup," said Sport Minister Nigel Huddleston.
"Despite working tirelessly to explore solutions that would allow us to go ahead as planned, circumstances beyond our control have meant that postponing the Rugby League World Cup until next year is the strongest option for staging a successful tournament."
The Rugby League Players Association (RLPA) said it acknowledged "the extremely difficult decision" to delay the World Cup and the "tremendous effort of the RLWC board, Jon Dutton, and the entire team to maintain the tournament's viability up to this point".
"We have worked exceptionally close with the RLWC team to date and want to thank them for engaging in such a collaborative process which has allowed the players to feel respected and valued throughout the RLWC planning," said RLPA chief executive officer Clint Newton.
Fresh Covid outbreaks in Australia have forced most states to reimpose restrictions, while the majority of coronavirus restrictions in England have been lifted despite a rise in cases - although those numbers appear to be falling.
The pandemic problem
There were concerns about players and staff having to quarantine for 14 days on their return to Australia, with the country's borders currently closed because of the pandemic.
Rugby league officials estimate about 400-500 players, staff and team officials from Australia's National Rugby League - representing several different countries - would be impacted by any quarantine measures on their return to the country after the tournament.
Those measures would mean players would only return to their NRL clubs two weeks before trial games for the 2022 season begin.
The number of those who would be affected is significantly higher when the women's and wheelchair events are taken into consideration.
The postponement will be a major blow to English rugby league, a sport that has been hit hard by the financial fallout of the pandemic.
The UK government has provided rugby league with more than £32m in loan support in the past year.
Australia, as 11-time and defending men's champions, were favourites to win the tournament in England, while 2008 winners New Zealand were again poised to be contenders.
The event, regarded as one of the most inclusive sports events ever hosted in Britain, was to be staged across 16 towns and cities across England.
St James' Park, home of Premier League football side Newcastle United, was scheduled to host the opening game between England and Samoa.
Manchester United's Old Trafford stadium was to host the men's and women's finals in a back-to-back spectacle on 27 November.
Analysis - 'It's now fingers crossed for 2022'
BBC rugby league correspondent Dave Woods
Australia's NRL clubs have got their way.
The postponement seemed inevitable once they decided, through the voice piece of the Australian Rugby League Commission, that they didn't want to allow their players to compete in a World Cup in England this year.
Covid is only the broad issue.
The risk of players being exposed to the virus in this country is a valid concern, despite the RLWC2021 organisers bending over backwards to ensure that protocols would have been in place to keep the tournament as safe as possible.
But at the heart of this is that those NRL clubs have only self-interest. They want to protect their own domestic competition going into the 2022 season, rather than seeing the bigger picture of what a World Cup could do for the international profile of the game.
It's to be hoped they will prove honourable when they say they will support a rearranged Rugby League World Cup.
With the number of Covid cases in Australia not yet reaching the numbers seen in other countries, and with their vaccine roll out programme a long way behind schedule, it's hard to gauge how badly the pandemic will hit that country in 2022. And indeed, whether a dramatic spike in cases over the next few months will again lessen their appetite to send players abroad.
In the meantime, some more incredibly hard work begins for the Rugby League World Cup organisers.
Stadiums will have to be rebooked. Cities and towns where the Men's, Women's and Wheelchair teams were going to be based will have to be re-primed in readiness for the delayed event. Broadcasters will have to reschedule.
This year's tournament had been over four years in the planning up to this point. Now they have to do a lot of the work again, but this time with less than 14 months to go.
Finances will be stretched because budgets were only due to run up to the end of November of this year and the government will be called upon to add to the £25m that it's already invested into the tournament.
But in the circumstances of the last few weeks, and the stance of the NRL clubs, Jon Dutton, the RLWC2021 chief executive and his board of directors, had little option but to call a halt to their desperate hard work to get the tournament on as planned.
It's now fingers crossed for 2022.
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