Real Madrid, Barcelona and Juventus face a two-season Champions League ban unless they withdraw from the European Super League and sign a settlement agreement with UEFA.
A disciplinary investigation has been opened by UEFA against the three clubs in connection to their involvement with the European Super League project.
The trio are the only clubs from the original 12 involved in the breakaway plans yet to formally withdraw.
The nine clubs who pulled out of the European Super League – including Manchester United, Manchester City, Liverpool, Chelsea, Arsenal and Tottenham – signed the Club Commitment Declaration with UEFA on Friday.
UEFA is confident the three rebel clubs, who have won 20 European Cups between them, will be forced to sign up soon.
The prospect of disciplinary action appeared inevitable last Friday when a statement confirming the peace accord with nine of the clubs ended: “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 breakaway league was abandoned within 72 hours of its announcement last month amid considerable fan protests, Government pressure, and player and manager rejection.
On Saturday, Real Madrid, Barcelona and Juventus hit out at “intolerable” pressure and threats to abandon the European Super League project, and vowed to “persevere” with the idea despite its considerable rejection.