Twelve of Europe's top clubs announced on Sunday they were launching a breakaway Super League, headed by Real Madrid president Florentino Perez.

AC Milan, Arsenal FC, Atletico Madrid, Chelsea, Barcelona, Internazionale, Juventus, Liverpool, Manchester City, Manchester United, Real Madrid and Tottenham Hotspur have all joined as founding clubs, the statements added.

Madrid president Perez said: "We will help football at every level and take it to its rightful place in the world. Football is the only global sport in the world with more than four billion fans and our responsibility as big clubs is to respond to their desires."

As part of the move, the clubs included would withdraw from the European Club Association and games would be played in the middle of the week, with the Super League governed by the founding clubs, the club statements indicated.

The agreement provides that the founding clubs will receive an upfront net grant of approximately €3.5 billion ($4.19 billion) in aggregate, the statements said.

ESPN sources said earlier on Sunday that up to 15 of Europe's biggest clubs are in talks to launch a so-called European Super League, planned to start in time for the 2023-24 season.

If the initiative is successful, which has already been rebuked by FIFA and numerous FAs throughout Europe, it would threaten the existence of the Champions League -- football's biggest club competition -- with UEFA due to announce on Monday a new 36-team format for the tournament designed to stave off attempts by the game's top clubs to break away.

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A women's Super League competition is also planned to be launched after the men's league is up and running, the statement said.

The format of the competition would be two groups of 10 playing home and away fixtures with the top three in each group qualifying for the quarter-finals. A play-off involving fourth and fifth placed teams will complete the final eight.

Juventus president Andrea Agnelli, vice-chairman of the new league, said the move would secure the long-term future of the game.

"Our 12 founder clubs represent billions of fans across the globe and 99 European trophies. We have come together at this critical moment, enabling European competition to be transformed, putting the game we love on a sustainable footing for the long-term future, substantially increasing solidarity, and giving fans and amateur players a regular flow of headline fixtures that will feed their passion for the game while providing them with engaging role models."

FIFA said on Sunday it disapproved of the breakaway competition called the European Super League as it was outside of international football structures.

"Against this background, FIFA can only express its disapproval to a 'closed European breakaway league' outside of the international football structures," a statement from football's world governing body read.

ESPN has been told by a person familiar with the blueprint that the proposed framework involves a total of 20 teams, with 15 permanent members who cannot be relegated.

Sources have told ESPN that New York-based investment bank JP Morgan will underwrite the project, with $6 billion distributed as loans to the teams.

Under pressure from the European Club Association, UEFA has drawn up plans to reshape the Champions League format, with the new-look competition due to be unveiled Monday, ahead of UEFA's executive committee summit in Switzerland this week.

UEFA criticised the plans in a statement and said: "UEFA, the English Football Association and the Premier League, the Royal Spanish Football Federation (RFEF) and LaLiga, and the Italian Football Federation (FIGC) and Lega Serie A have learned that a few English, Spanish and Italian clubs may be planning to announce their creation of a closed, so-called Super League.

"If this were to happen, we wish to reiterate that we - UEFA, the English FA, RFEF, FIGC, the Premier League, LaLiga, Lega Serie A, but also FIFA and all our member associations - will remain united in our efforts to stop this cynical project, a project that is founded on the self-interest of a few clubs at a time when society needs solidarity more than ever.

"We will consider all measures available to us, at all levels, both judicial and sporting in order to prevent this happening. Football is based on open competitions and sporting merit; it cannot be any other way.

"As previously announced by FIFA and the six Federations, the clubs concerned will be banned from playing in any other competition at domestic, European or world level, and their players could be denied the opportunity to represent their national teams.

"We thank those clubs in other countries, especially the French and German clubs, who have refused to sign up to this. We call on all lovers of football, supporters and politicians, to join us in fighting against such a project if it were to be announced. This persistent self-interest of a few has been going on for too long. Enough is enough."

Planned to come into force in 2024, the remodelled Champions League would involve 36 teams playing 10 group games rather than six. The biggest clubs would also receive an increased share of prize money.

Sources told ESPN that UEFA plan to press ahead with their announcement Monday, and that any breakaway league remains a distant prospect, with national associations UEFA and FIFA both needing to sanction the proposal.

Meanwhile, the European Clubs' Association issued a statement in which it reiterated commitment to working with UEFA on competition reform, adding that a "closed super league model ... would be strongly opposed."

Serie A called an emergency board meeting on Sunday to discuss a newspaper report saying broadcaster DAZN is involved in new plans for the breakaway league, a source told Reuters.

The meeting was called by league president Paolo Dal Pino, and Italian newspaper Corriere dello Sport reported that DAZN, which is owned by billionaire Len Blavatnik's Access Industries, has been working on the formation of the league for some time.

The report claims the meeting is being attended remotely, with the three Serie A clubs who could potentially be part of the new project: Juventus, Inter Milan and AC Milan.

FIFA has earlier said that players who feature in any breakaway European Super League would be banned from playing in FIFA competitions, including the World Cup.

It caps a tumultuous week for Serie A after seven clubs submitted a written request for Dal Pino to resign over issues that include his management of plans to sell a stake in the league's media business.

The plans to expand the Champions League are also likely to meet opposition from supporters; ESPN reported last week that fans' groups have already registered their anger over UEFA's proposed changes.

On Sunday, a statement from the Premier League condemned the breakaway plans.

It read: "The Premier League condemns any proposal that attacks the principles of open competition and sporting merit which are at the heart of the domestic and European football pyramid.

Fans of any club in England and across Europe can currently dream that their team may climb to the top and play against the best. We believe that the concept of a European Super League would destroy this dream.

"The Premier League is proud to run a competitive and compelling football competition that has made it the most widely watched league in the world. Our success has enabled us to make an unrivalled financial contribution to the domestic football pyramid.

"A European Super League will undermine the appeal of the whole game, and have a deeply damaging impact on the immediate and future prospects of the Premier League and its member clubs, and all those in football who rely on our funding and solidarity to prosper.

"We will work with fans, The FA, EFL, PFA and LMA, as well as other stakeholders, at home and abroad, to defend the integrity and future prospects of English football in the best interests of the game."

Information from Reuters was also included in this report.