https://www.bbc.co.uk/sport/rugby-league/46763920Challenge Cup holders Catalans Dragons are considering their place in the 2019 competition after being ordered to pay a £500,000 deposit to enter.
The French club became the first team from outside England to win rugby league's oldest trophy.
Catalans have asked the Rugby Football League to "reconsider its demand", which applies to all non-English teams.
Owner Bernard Guasch said they want to defend the cup, but added "it would be irresponsible to accept" the decision.
"The players would be very frustrated not being able to defend their title and we hope that we'll have an answer as soon as possible," Guasch said.
The deposit is understood to have been introduced to help cover any dip in revenue raised from the RFL's flagship competition.
While Catalans made history by winning in 2018, the final against Warrington was played in front of 50,672 - Wembley Stadium's lowest Challenge Cup final crowd since World War Two.
Already, fellow French club Toulouse and Canadian side Toronto - the first team from across the Atlantic to play in the Challenge Cup - have decided not to enter the competition. Both teams play in England's second division.
Red Star Belgrade, however, will remain in the competition and not need to pay the bond as they are an amateur team that will play their opening two rounds away from home, should they progress.
The RFL confirmed issues about Catalans' cup defence were raised in December.
"We have been surprised and disappointed by the uncertainty over the Catalans Dragons participation in the 2019 Challenge Cup, which surfaced just before Christmas," a statement said.
"We have been in discussions with the club since then, and will continue those discussions to search for a solution."
Analysis
Matt Newsum, BBC Sport rugby league reporter
The prospect of the Challenge Cup holders refusing to defend their title, because of issues related to bonds and financial input, is one which has left most rugby league fans scratching their heads.
Catalans' success at Wembley last year was one of the highlights of any season, let alone 2018, a genuine moment of brightness and progress in a sport which needs as many newsworthy crossover moments as it can muster.
However, amid the excitement there were concerns at the level of the attendance at that showpiece event, one of the knock-on effects of fewer Catalans fans making the trip.
It is not the only factor though. One of the issues comes from the RFL acquiring the opportunity to sell the ring of 'Club Wembley' seats that previously were counted as part of the attendance. The slide was felt in 2017 too.
With a number of big events in London over the August Bank Holiday weekend such as the Notting Hill Carnival and Premier League football - travel and accommodation prices are ramped up. Also the impact of track maintenance work massively affecting the West Coast Mainline must be acknowledged. Expense and inconvenience for fans has to be considered. It did dissuade fans from travelling.
Changes have been made to the date of the final going forward in order to arrest this issue, moving to July to avoid such clashes and cost implications.
There is some sympathy at the RFL seeking to cover its back financially, but there is mostly the sense that this was a massive 'own goal' for the governing body.
The question ought to be asked: If Wembley proves too expensive for the Challenge Cup, then perhaps it needs to rethink where the final is held?
) who support Premiership football teams, and who just can't wait for the next episode in the farce that is RL. Whilst they may admire the players, they see our governing body as the comedy gift that continues to give!
