The three hold-out clubs could face sanctions including being banned from the Champions League.
The three remaining European Super League rebels stepped up their criticism of UEFA on Saturday, with Barcelona, Real Madrid and Juventus denouncing intolerable threats for their refusal to back down on the prospect of a breakaway competition.
Nine of the 12 Super League clubs have formally renounced the breakaway and committed to the existing European competitions but they will have to give up 5% of UEFA revenue for one season.
"We regret to see that our friends and founding partners of the Super League project have now found themselves in such inconsistent and contradictory position when signing a number of commitments to UEFA yesterday,'' Barcelona, Madrid and Juventus said in a joint statement.
"We have the duty to act in a responsible manner and persevere in the pursuit of adequate solutions, despite the unacceptable and ongoing pressures and threats received from UEFA.''
The trio risks being banned from the Champions League as UEFA pursues a disciplinary process against them for not disavowing the Super League and being reintegrated into the existing system.
"The founding clubs have suffered, and continue to suffer, unacceptable third-party pressures, threats, and offenses to abandon the project and therefore desist from their right and duty to provide solutions to the football ecosystem via concrete proposals and constructive dialogue,'' Barcelona, Madrid and Juventus said. "This is intolerable under the rule of law.''
The Super League project imploded three weeks ago after the English clubs - Arsenal, Chelsea, Liverpool, Manchester United, Manchester City, and Tottenham - backed out within 48 hours after a furious backlash from the fans and the British government.
Atletico Madrid, AC Milan, and Inter Milan have also officially signed up to a settlement with UEFA to only participate in the existing open European competitions.
The nine clubs will make a combined payment of 15 million euros for what UEFA called a “gesture of goodwill” to benefit children, youth, and grassroots football. They have also accepted UEFA withholding 5% of revenue for the next season they play in their club competitions.
The clubs have also agreed to be fined 100 million euros if they seek again to play in an unauthorized competition or 50 million euros if they breach any other commitments to UEFA as part of the settlement.
“The measures announced are significant, but none of the financial penalties will be retained by UEFA,” said Aleksander Čeferin, the UEFA president.
"They will all be reinvested into youth and grassroots football in local communities across Europe, including the UK. These clubs recognised their mistakes quickly and have taken action to demonstrate their contrition and future commitment to European football.
"The same cannot be said for the clubs that remain involved in the so-called ‘Super League,’ and UEFA will deal with those clubs subsequently.”
Ceferin previously told The Associated Press that the clubs refusing to renege on the Super League could be banned from UEFA's competitions.