Michel Platini, the president of European football's governing body, urged under-fire FIFA president Sepp Blatter to stand down when the pair met on Thursday.
Blatter is overseeing a crisis at FIFA amid fresh corruption allegations emerging from separate inquiries by the U.S. Department of Justice and the Swiss government.
However, the 79-year-old has refused to quit and still intends to stand against Prince Ali Bin Al Hussein in Friday's presidential vote.
"I have had enough -- enough is enough, too much is too much. I am the first to be disgusted," Platini told a news conference. "I told Mr Blatter 'we started together and now I am asking you to step down as we cannot continue this way.'
"He told me 'It's too late, I can't today all of sudden leave when Congress starts this afternoon.'''
Platini also said he was convinced Prince Ali could win, adding: "A very, very big majority of UEFA associations will vote for Prince Ali -- a minimum of 45 or 46 [out of 53], and I try to convince more.''
The UEFA chief warned, however, that Blatter's decision to stay meant his support is still daunting, but that there was now more democracy with confederations not voting en bloc.
"If he has decided to stay on, it means he is still strong,'' he said. "But there's a renewal of democracy in the African zone to vote freely. As I said to Europe, vote freely -- but vote for Prince Ali.''
When asked if a boycott of FIFA competitions was a possibility if Blatter wins, Platini replied: "UEFA associations will meet in Berlin next week. We will be open to all options."
Pressed further on the prospect of a World Cup boycott, Platini added: "There may be proposals. I honestly don't wish that."
Information from the Press Association was used in this report.