Fifa president Sepp Blatter has told an emergency meeting of football's governing body he will not quit, amid growing political pressure over a corruption scandal.
Seven top Fifa officials were arrested in Zurich on Wednesday, among 14 people indicted by US prosecutors.
UK PM David Cameron urged Mr Blatter to resign but Russian President Vladimir Putin has backed him for a fifth term.
Fifa's congress has opened. The vote for president will go ahead on Friday.
Michel Platini, the head of Uefa, the European football governing body, had asked Mr Blatter to resign after the crisis talks in Zurich, which involved heads of the six international confederations. The president refused.
Mr Platini later said that if Mr Blatter were re-elected, Uefa might have to discuss its relations with Fifa.
Key sponsors have expressed concern over twin corruption investigations by both the US and Swiss authorities.
The emergency meeting was Mr Blatter's first appearance since the crisis began on Wednesday.
He was not among the 14 people who were charged by the US authorities on Wednesday with racketeering, fraud and money laundering.
At a Uefa news conference later, Mr Platini said he had asked Mr Blatter "as a friend" to resign, saying: "I have had enough - enough is enough, too much is too much.
"I say these things with tears in my eyes. I don't like it this way. But there are just too many scandals."
But the president told Mr Platini it was too late, as Fifa's congress was about to start. The opening ceremony has now begun in Zurich, with Mr Blatter in attendance.
Uefa agreed at its meeting on Thursday to throw its weight behind Jordan's Prince Ali bin al-Hussein, Mr Blatter's only challenger, in Friday's vote.
Mr Platini said that if Mr Blatter won, Uefa could hold an extraordinary meeting in Berlin at the time of the Champions League final.
When asked if this could include withdrawing from Fifa competitions, Mr Platini said: "We will raise all possibilities."
Pressed on the possibility of a World Cup boycott, he said: "There may be proposals. I honestly don't wish that."
Mr Platini said the other confederations had wanted the vote to go ahead "and let the best man win".
The Confederation of African Football (Caf) said in a statement that it opposed any delay to the vote.
Meanwhile, Britain's David Gill said he would not take up his post on Fifa's executive committee if Mr Blatter were re-elected.
French Foreign Minister Laurent Fabius had earlier urged a delay in the vote, saying Fifa's current image was disastrous.
Mr Putin, however, said the allegations against Fifa were a clear attempt by the US to stop Mr Blatter's re-election.
Fifa on Wednesday provisionally banned from football-related activity 11 of the 14 people charged in the US. On Thursday it added another, Aaron Davidson.
Some of the 14 are accused of receiving bribes to influence the outcome of bids to stage football tournaments, such as the 2010 World Cup in South Africa and the 2016 Copa America in the US.
South African government officials have denied the claim.
One of those indicted, Chuck Blazer, the former top American official at Fifa, has already pleaded guilty to four charges and has been a co-operating witness for the FBI since he quit football in 2013.
In addition to Coca-Cola and Visa, major sponsors Adidas, McDonald's, Hyundai Motor, Budweiser and Gazprom are also pressing Fifa to take immediate action to restore its reputation.
Swiss prosecutors plan to interview 10 Fifa executive committee members as part of a separate investigation into the bidding process for the World Cup tournaments in 2018 in Russia and 2022 in Qatar.