FIFA president Gianni Infantino condemned the European Super League as he warned clubs involved they "cannot be half in or half out" and must fully commit to the breakaway competition.

Twelve elite clubs announced on Sunday their plans to launch a tournament to rival the Champions League in which they would be assured of qualification.

Real Madrid, Barcelona and Manchester United, among others, would compete in the Super League every season without risk of demotion.

The news has prompted a strong reaction throughout the football world, with governing bodies, rivals clubs, players, coaches and fans critical of the idea and its anti-competitive format.

An initial FIFA statement on Sunday read: "FIFA can only express its disapproval to a 'closed European breakaway league' outside of the international football structures."

Infantino, FIFA president since 2016, had not subsequently discussed the Super League in public until Tuesday's UEFA Congress, however.

But he made clear in Montreux, Switzerland, that the clubs involved could not continue in their domestic leagues, as proposed, while bans from international football for players at those clubs have been threatened.

"At FIFA, we can only strongly disapprove the creation of the Super League, which is a closed shop, which is a breakaway from the current institutions, from the leagues, from the associations, from UEFA, and from FIFA," Infantino said.

"There is a lot to throw away for maybe a short-term financial gain of some. People need to think very carefully. They need to reflect and they need to assume responsibility.

"If some elect to go their own way, then they must live with the consequences of their choice. They are responsible for their choice.

"Concretely, this means either you are in or you are out. You cannot be half in or half out."

Gianni Infantino says FIFA must be open to revolutionising the international calendar, after Arsene Wenger proposed radical changes.

Speaking on beIN SPORTS this week, former Arsenal manager Wenger claimed more focus had to be put on FIFA's flagship competitions, including the World Cup.

The Frenchman is currently serving as FIFA's chief of global football development.

Wenger put forward a plan to host major tournaments such as the World Cup and European Championship every two years, to give more players the opportunity to play at these events during their prime years.

Such changes would mean major alterations to the calendar, but Infantino insists FIFA will rule nothing out, and decisions could be taken within the next 12 months.

"We need to be open to everyone, to everything, to every proposal, every idea," said the FIFA president.

"Arsene Wenger is not only a successful and brilliant manager, he is a professor of football but besides that we have, of course, our bodies and we will debate and discuss the calendar, starting now, because we need to come to a decision in the next few months, the sooner the better, by the end of the year or in the course of next year, for everyone to be able to plan."

The international schedule is not the only item up for debate, with Infantino also interested in a possible merger of North America's leading leagues – Major League Soccer (MLS) and Liga MX.

MLS commissioner Don Garber commented in December that a merger was "a long way away", while FIFA has previously ruled out leagues spread across regions or continents, rather than individual countries.

However, Infantino seemingly sees things differently, as he stressed the need for other areas of the globe to challenge the quality on show in Europe.

"I think the potential in the United States and Mexico is enormous, each country by itself," he said.

"But of course if you could bring those two together that would be incredible and that could quite well be the best league in the world.

"Any discussion about organising such a competition, of course respecting the rules of member associations and FIFA and with the agreement of all stakeholders, any discussion in that respect is interesting and we see that in a positive light.

"Of course if we want club teams to be at the highest level around the world and not just in Europe, we need to have new ideas.

"We see the potential in North America, the economic potential and the potential in footballing terms. I trust them to take the best decisions in that regard."