The 12 European clubs pursuing a Super League have told the leaders at FIFA and UEFA that legal action is already being pursued to stop them from action intended to thwart the launch of the breakaway competition, according to a letter obtained on Monday by the Associated Press.

The letter was sent by the group of English, Spanish and Italian clubs to FIFA President Gianni Infantino and UEFA counterpart Aleksander Ceferin saying the Super League has already been underwritten by a grant of €4 billion ($5.5bn) from JP Morgan.

- Super League Q&A: What does this mean for European football?
- Stream ESPN FC Daily on ESPN+ (U.S. only)

UEFA warned the Super League clubs, including Barcelona, Juventus and Manchester United, after leaks of their plans on Sunday that legal action would be taken against rebel clubs and said they would be barred from existing domestic competitions like La Liga in Spain and the Premier League in England.

"Your formal statement does, however, compel us to take protective steps to secure ourselves against such an adverse reaction, which would not only jeopardise the funding commitment under the Grant but, significantly, would be unlawful," the Super League clubs wrote to Infantino and Ceferin. "For this reason, SLCo (Super League Company) has filed a motion before the relevant courts in order to ensure the seamless establishment and operation of the Competition in accordance with applicable laws."

The courts were not named.

"It is our duty, as SLCo's board members, to ensure that all reasonable actions available to protect the interests of the competition and our stakeholders are duly taken, given the irreparable damage that would be suffered if, for any reason, we were deprived of the opportunity to form promptly the competition and distribute the proceeds of the grant," the Super League letter continued.

The breakaway was launched just as UEFA, which runs European football, thought it had agreement on an expansion of the Champions League from 2024. Now, the same officials who backed the plans have decided to go it alone while claiming the existing competitions could remain -- despite losing their most successful teams, including record 13-time European champion Real Madrid.

"The competition is to be played alongside existing domestic league and cup competitions, which are a key part of European football's competitive fabric," reads the Super League letter to Infanatino and Ceferin. "We do not seek to replace the UEFA's Champions League or the Europa League but to compete with and exist alongside those tournaments."

UEFA are due to announce on Monday a new 36-team format for the Champions League that was designed to stave off attempts by the game's top clubs to break away.