The beleaguered 79-year-old president remained closeted in his office as global headlines slammed the "World Cup of fraud" and some calls were made for him to stand down. Blatter remains favourite to win an election on Friday however.

Credit card giant Visa said it would "reassess" its sponsorship of FIFA unless it takes immediate action after the arrest of top FIFA leaders accused by US authorities of taking huge bribes.

While Swiss police are investigating the award of the 2018 and 2022 World Cups to Russia and Qatar, US documents indicate that South Africa paid bribes to FIFA officials to secure the 2010 World Cup.

Visa said that unless FIFA rebuilds a corporate culture with "strong ethical practices" at its heart, "we have informed them that we will reassess our sponsorship". Coca-Cola, Adidas, McDonald's and Budweiser all spoke out against the corruption scandal. Corporate backers provide hundreds of millions of dollars to FIFA's finances.

FIFA's annual congress starts in Zurich on Thursday but its leader stayed out of the public eye as the corruption storm grew.

He failed to make expected appearances at regional confederation meetings before the congress. He also cancelled an expected appearance at a medical conference. FIFA's chief medical officer Jiri Dvorak said Blatter had to manage the "turbulence" hitting the organisation.

Some European leaders even renewed calls for Blatter to resign. But FIFA remain adamant that the congress and vote will go ahead. And African and Asian confederations have reaffirmed their support for Blatter. Asian Football Conderation members hold 47 of the 209 votes in the FIFA election, behind the Confederation of African Football (56 votes) and UEFA (54).

Seven football officials, including two FIFA vice presidents, remained in Swiss custody on Thursday after their arrest at the FIFA hotel in Zurich early Wednesday. Six of the seven have indicated they will fight extradition to the United States, Swiss authorities said.

US authorities said nine football officials in all were among 14 people facing up to 20 years in jail if found guilty in the long-running corruption case involving more than USD 150 million in bribes. US authorities indicated that more charges could follow.

Blatter said it was a "difficult time" for the world body, and added that he would not tolerate misconduct by FIFA officials. FIFA vice presidents Jeffrey Webb - the current CONCACAF chief - and Eugenio Figueredo, a former head of the South American confederation, were among the seven arrested by Zurich police.

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