Top players could be banned from the World Cup if they take part in any breakaway competition, FIFA president Gianni Infantino has warned, saying: "You are either in or you are out."
German magazine Der Spiegel reported last week that Bayern Munich and their chairman Karl-Heinz Rummenigge attempted to lead some of the continent's biggest clubs into a new competition.
The allegations, which were based on documents purportedly attained from whistleblowers Football Leaks, have been strongly denied by both Bayern and Rummenigge.
European Leagues - an organisation that acts on matters of common interest regarding clubs from the 32 professional leagues it represents - has already spoken out against the idea of a "closed and franchised style" competition.
And Infantino says there could be wider implications for any players who join their clubs in any prospective European Super League.
"You are either in or you are out," he told reporters. "If there are players who don't play in organised football, they don't play organised football, and that encompasses everything - national leagues, confederation competitions, the Euros and the World Cup."
FIFA legal director Alasdair Bell added: "The idea is if you break away, you break away – you don't keep one foot in and one foot out.
"That would be the general approach we would follow, but of course lawyers can debate this for a long time."
The reports come at a time of friction between FIFA and UEFA over plans to expand the Club World Cup, and Infantino insists those changes are the solution to quell the threat of a breakaway.
"The Club World Cup is the answer to any attempt to think even about any sort of breakaway leagues," he commented.
"If the price to pay is to give proper revenues to a club participating in a Club World Cup but this allows us to... give $1million to Haiti who has nothing, or to Mongolia who has three time zones but only two football pitches, well then we should be, I think, doing that."