The European football governing body Uefa on Friday announced sanctions, including financial punishments, against nine of the 12 clubs behind the aborted European Super League project.
However, three clubs, Barcelona, Real Madrid and Juventus, did not sign the declaration meaning that they are likely to face more sanctions.
Uefa said it "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 statement concluded.
The nine clubs that opted out of the project (Tottenham, Arsenal, Manchester City, Manchester United, Chelsea, Liverpool, Atletico Madrid, Inter Milan and AC Milan) have agreed to a series of "reintegration measures".
"These clubs recognised their mistakes quickly and have taken action to demonstrate their contrition and future commitment to European football," said Uefa president Aleksander Ceferin.
"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."
The nine have agreed to forego five percent of their revenue from Uefa competitions for one season and pay, between them, ($18.25 million) donation to support grassroots and youth football in Europe.