FIFA is currently exploring the idea of doubling the frequency of the competition but the UEFA chief is worried about the impact of such a move
UEFA has "grave concerns" about plans to hold the World Cup every two years, president Aleksander Ceferin says.
The idea to make the tournament a biennial event has gained traction since it was first raised at a FIFA congress in May and the governing body is carrying out a feasibility study.
But Ceferin is upset by FIFA's lack of consultation with UEFA and the impact that such a move would have.
What has been said?
Ceferin expressed his concerns in response to a letter from Football Supporters Europe, writing to executive director Ronan Evain: "UEFA and its national associations also have serious reservations and grave concerns surrounding reports of FIFA’s plans.
"Considering the major impact this reform may have on the whole organisation of football, there is widespread astonishment that FIFA appears to be launching a PR campaign to push its proposal whilst any such proposals haven’t been presented to confederations, national associations, leagues, clubs, players, coaches, clubs and all the football community.
"As one concrete example amongst so many, it is imperative to highlight the concerns shared across the footballing world regarding the impact a biennial FIFA World Cup would have on the international match calendar and, prominently in this context, on women’s football."
He added: "Your letter and the concerns it raises on behalf of supporters across Europe regarding FIFA’s potential plans to hold the FIFA World Cup every two years, are extremely valid and important.
"Allow me to assure you that UEFA stands with you and the fans on this important issue. We must work together to defend the interests of the game and reinforce the position of fans as key stakeholders."
Why does FIFA want a World Cup every two years?
FIFA's members approved the launch of a feasibility study about staging the World Cup every two years instead of four after the proposal was submitted by the Saudi Arabian Football Federation.
President Gianni Infantino suggested he is in favour of the change after the FIFA congress in May, saying at a press conference: "You don’t need to be an Einstein to know that if you have the World Cup every two years you double the revenue.
"We have to go into these studies with an open mind. We know about the value of the World Cup and the impact of the World Cup."
The plan is also backed by ex-Arsenal manager Arsene Wenger, who is currently FIFA's chief of global football development.
The Frenchman said in July that it would lead to fewer international breaks during the season and lower the risk of injury to players.
Wenger denies that there is any financial incentive behind the idea, L'Equipe this week: "The principle would be a grouping of qualifiers every year, and at the end of the season a major competition, World Cup or continental championship.
"The idea is really to improve the level of play and competitions, there’s no financial incentive behind it, especially as FIFA redistributes the money to all of the federations around the world to develop football in their countries."