"It's very difficult to say" he told a news conference in Belfast following a two-day annual meeting of the International Football Association Board .
He said: "It is easy to destroy a reputation, it takes one second, it takes years to build one."
Michael Garcia, the former U.S. prosecutor, led FIFA's investigation into the bidding processes for the 2018 and 2022 World Cups.
A number of European officials have called on FIFA to publish Garcia's full report, but the governing body said it could not release it to the public for legal reasons.
Valcke added that the World Cup hosts for 2018 and 2022, Russia and Qatar, were final and would not be reviewed.
He also said reports that Sony were not planning to renew its sponsorship contract with FIFA had nothing to do with the governing body's reputation.
"I disagree, 1000 percent, I disagree. It has nothing to do with FIFA's reputation," he said. "It has nothing to do with what has happened over the last weeks. It has nothing to do with the situation we are facing."
He said FIFA had spoken with sponsors and partners directly, and added: "the value of a World Cup, the value of what we are doing is still the same, the value of the work of the administration of FIFA is still the same -- we are doing a great job."
He said the non-publication of the full report into the bid processes was down to promises of anonymity given to 75 people who had given evidence to the investigation. He gave up his own anonymity by saying he was one of the 75.
Image: Jerome Valcke
Photograph: Alexandre Schneider/Getty Images
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