The three remaining Super League members face a potential two-season ban from the Champions League, unless they withdraw from the breakaway division and sign a settlement agreement.
Barcelona, Real Madrid and Juventus are the only teams not to have backed down from the proposed SL, and have hit out at the other nine teams for bending to UEFA's 'unacceptable' pressures and threats, which included suspension from European competition.
And Sky Sports reports that UEFA are ready to hit the trio with a two-season ban from the Champions League, should they decide not to follow the nine other clubs in signing the Club Commitment Declaration.
UEFA began preparations to open an official case against Barça, Madrid and Juve on Friday, after they failed to convince the rebels to abandon their plans and fall in line. The governing body then announced in a statement that it was ready to 'take whatever action it deems appropriate' against the three teams, as tensions continue to rise.
"UEFA has reserved all rights to take whatever action it deems appropriate against those clubs that have so far refused to renounce the so-called 'Super League'.
"The matter will promptly be referred to the competent UEFA disciplinary bodies."
The SL was formed and abandoned in the space of 72 hours, after Manchester City, Manchester United, Chelsea, Liverpool, Arsenal and Tottenham Hotspur all withdrew following major protests from supporters up and down the country.
Milan, Inter and Atletico Madrid eventually followed suit, leaving only three clubs who were not prepared to give up on their dreams of an elite European league.
As punishment, the nine clubs will donate a combined £13m to benefit children and grassroots football across Europe, while also facing a potential £87m penalty should they attempt to join a breakaway league again in the future. UEFA will also withhold and redistribute five percent of each club's potential revenue from European football for one season.
Undeterred, Madrid, Barça and Juve released a joint statement on Saturday, stressing that the SL had been created for the 'good of football', but their pleas have fallen on deaf ears around the world. I Bianconeri also face expulsion from Serie A, as the Italian FA looks to take a similarly hard stance against the former league champions.