LAUSANNE (AFP) - After powerful Fifa sponsors demanded his immediate resignation, a key question surrounded Sepp Blatter on Saturday: Can the sleaze-tainted president of world football's governing body survive until his planned departure in February?

Coca-Cola, McDonald's, Visa and Budweiser in separate statements Friday called for Blatter to go, one week after Swiss prosecutors opened a criminal investigation against the 79-year-old over mismanagement.

Blatter remained defiant, saying his departure would not best serve Fifa's interests and that he did not plan to resign before February, when a special election has been called to choose his replacement.

Blatter's position may prove untenable.

Exposure of the rot within Fifa had already sparked widespread calls for immediate change, but the rare display of unity from four major corporations marked the first time key financial backers had explicitly demanded Blatter's resignation.

"The sponsors have the financial power to force change at Fifa," said Cobus de Swardt, managing director of the corruption watchdog Transparency International.

BLATTER CLOSELY TIED TO COCA-COLA

The unprecedented crisis within world football began on May 27, when nine Fifa officials and five sports marketing executives were charged by the US Justice Department over bribery worth more than US$150 million dating back to 1991.

Blatter was re-elected as Fifa's president days later, but on June 2, made the shock announcement that he was prepared to go - on a timeline that he subsequently laid out.

For Fifa's powerful sponsors, that timeline became unacceptable after Switzerland revealed evidence of murky financial dealings directly linked to Blatter.

The Coca-Cola Company said Fifa's reputation was deteriorating "every day that passes" with Blatter in office.

"Coca Cola is more than a valued sponsor, they are the foundation of Blatter's position in Fifa," Patrick Nally, a prominent sports marketing executive who has previously partnered with Fifa, said on Twitter.

Coca-Cola's partnership with Fifa coincided with Blatter's arrival as a public relations executive at the organisation in 1975.

Blatter's influence convinced Coca-Cola to pay some US$10 million, notably to sponsor the 1977 Youth World Cup in Tunisia and become the official sponsor of the 1978 World Cup that was held and won by Argentina.

The World Cup partnership, believed to currently be worth tens of millions of dollars per year, remains in place and was extended through to 2022.

Visa, another top-tier World Cup sponsor, said "no meaningful reform can be made under Fifa's existing leadership," with similar comments coming from McDonald's and Budweiser's parent company, Anheuser-Busch InBev.

Key sponsors based outside the US have not gone as far.

Germany-based Adidas reiterated its stance that change within world football was vital, but did not comment directly on Blatter.

German Justice Minister Heiko Maas, however, said Blatter should go to clear the way for a new beginning in the sport.

"Every day on which #Blatter is still #Fifa president is a bad day for football," he wrote on Twitter.

There was no immediate comment from Hyundai or Gazprom.

In a statement released after the resignation call from Coca-Cola, Blatter's attorney Richard Cullen said his client "believes firmly that his leaving office now would not be in the best interest of Fifa nor would it advance the process of reform and therefore, he will not resign."

CRISIS GETS DEEPER

Fifa's leadership is facing crises on various fronts, aside from the US indictments and the Swiss probe that is targeting Blatter but which has also implicated the front-runner to replace him, European football chief Michel Platini.

Blatter's former right-hand man, secretary general Jerome Valcke, was suspended last month over allegations that he was aware of a black market ticket scheme surrounding the 2014 World Cup. Valcke denied the claims.

Meanwhile, Fifa's own ethics committee could suspend the president at any time, as the independent panel typically probes any official who is subject to even initial suspicion, a tag which certainly applies to Blatter.

But, given the financial heft of the companies involved, some believe the resignation demand from the four top sponsors will make it impossible for the embattled Swiss national to hang on.

"It is public statements (from sponsors) that can and will force real reform, despite Blatter's obvious desire to stay at Fifa," Transparency International's De Swardt said.