Uefa on Friday announced sanctions, including financial punishments, against nine of the 12 clubs behind the aborted Super League project, after the clubs “apologised” and acknowledged “a mistake”.

The governing body of European football said that “in a spirit of reconciliation” the nine clubs had agreed to a “Club Commitment Declaration” and accepted a five percent cut in their European revenue for one season.

However, three clubs, Barcelona, Real Madrid and Juventus, did not sign the declaration.

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.

Some media have reported that Uefa is contemplating a two-year ban from European competition for the three holdouts, the maximum its rules allow.

However, their options are clouded by a ruling from a commercial court in Madrid on April 20.

The court banned Uefa and Fifa from making any moves to block a Super League or taking any disciplinary measures against the clubs, players or officials involved.

It is also unclear what penalties the clubs that have withdrawn may owe to the remaining clubs for breaking their agreement to join the Super league.

The nine clubs that opted out of the project – Tottenham, Arsenal, Manchester City, Manchester United, Chelsea, Liverpool, Atletico Madrid, Inter Milan and, the last to withdraw, 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, a 15-million-euro ($18.25 million) donation to support grassroots and youth football in Europe.

‘Sincere apology’

A spokesperson for Manchester United confirmed the Glazer family, which owns the club, would cover their club’s share of both sums.

They also committed to participating in UEFA competitions for which they qualify and agreed to pay fines of 100m euros if they ever seek to play in an “unauthorised” competition.

“It takes a strong organisation to admit making a mistake especially in these days of trial by social media. These clubs have done just that,” said Ceferin.

“In accepting their commitments and willingness to repair the disruption they caused, UEFA wants to put this chapter behind it and move forward in a positive spirit.”

The English Football Association said in a statement that it was “delighted” that the six English clubs had committed to Uefa’s competitions and suggested that it too might punish the clubs.

“The FA has an ongoing inquiry into the involved of the six English clubs and we have formally requested all relevant information and evidence regarding their participation,” the statement.

“Once we have the required information, we will consider what appropriate steps to take.”

Earlier on Friday, Manchester United co-chairman Joel Glazer wrote to his club’s fans saying he was “personally humbled” by their reactions and understood “why our initial support for the European Super League left you feeling angry and let down.”

“I would like to reiterate my sincere apology for the mistakes that were made,” he said.