Aleksander Ceferin, a candidate to replace Michel Platini as UEFA president, warns that a European 'Super League' would cause a major rift between the governing body and the clubs involved.
Discussions have been ongoing between UEFA and the continent's major clubs about potential changes to the format of the Champions League.
Any changes are designed to prevent the bigger clubs breaking away and forming a 'Super League', with some clubs said to be unhappy with the financial disparity growing across the continent following the Premier League's lucrative new television deal.
But Ceferin, president of the Slovenian FA, wants Europe's clubs to remain together, citing fears of a potential "war" between those involved and UEFA.
"One of the main issues awaiting the next UEFA president is relations to the big clubs," he said in quotes reported by BBC Sport.
"My firm opinion is that some kind of closed super league with just a few clubs in, without the possibility for the others to enter, is out of the question.
"It will mean a kind of war between UEFA and the clubs.
"If they want more revenues we should work on it. It is possible. The Champions League is the best sports product in the world, for sure. But it doesn't generate the most money. So we should include them [the clubs] more."