Europe's top clubs are discussing possible changes to the Champions League but have played down talk of a breakaway 'super league'.
The European Clubs' Association (ECA) said it will work with Uefa on any "improvements" before 2018.
ECA boss Karl-Heinz Rummenigge has suggested "a tournament consisting of 20 teams from Italy, England, Spain, Germany and France".
Currently, 78 teams qualify from the 54 member leagues across Europe.
After preliminary qualifying rounds, 32 teams enter the group stage.
Following a meeting on Tuesday, Rummenigge said that "stagnation means regression" but promised to "find a good and balanced solution".
ECA senior vice-chairman Umberto Gandini said a review into the tournament's format would take six to nine months and would look to make the competition "more and more attractive".
Gandini said there was not yet an "understanding" that the Champions League would have to change but added: "We will listen to the main actors of the competition and Uefa itself and find out what is best.
"It may be just a slight change to the access list, it may be many aspects of the competition that can be reviewed and adjusted."
The ECA represents more than 200 clubs, including the likes of Real Madrid, Barcelona, Juventus, Bayern Munich, Manchester United and Chelsea.
There have been suggestions that these clubs should get direct entry into Europe's elite club football tournament, rather than through their domestic league position the previous season.
Rummenigge, who is chief executive of Bayern Munich, told a German newspaper last month: "A super league outside of the Champions League is being born. It will either be led by Uefa or by a separate entity, because there is a limit to how much money can be made."
Changes to European club competitions can only be made after three-year cycles, with the current one finishing after 2017-18.