JOHANNESBURG (Reuters) -- FIFA general secretary Jerome Valcke said on Thursday he did not believe allegations of a Russian-Spanish match-fixing plot at the World Cup, but that it was vital to ensure the tournament was above suspicion.

"I can't imagine it is true," Valcke said of the reported allegations by David Triesman, former chairman of the Football Association and head of the bid for the 2018 World Cup.

He also told a press lunch it was too early to assess the impact of the affair on England's bid to host that tournament and the next one in 2022.

Triesman quit this week after the secretly recorded allegations were made public in the Mail on Sunday. He was quoted saying rival bidders Spain and Russia conspired to bribe referees at next month's World Cup in South Africa.

Asked how much the scandal had damaged England's bid, Valcke said: "It is too early and it is quite difficult to see what is the potential impact on the bid."

Referring to when the winning bids will be chosen for 2018 and 2022 in December, he added: "We have six months. In six months a lot of things can happen."

Valcke said it was imperative to ensure there could be no suggestion of bribery or corruption at the 2010 World Cup.

FIFA was working with Interpol to see if there was any substance to the allegations and he expected a first report from his ethics committee on the affair by the end of this week.

"We will put in place a system where I hope we can see that nothing can happen during the World Cup," Valcke said.

"We have to protect the World Cup, it is our most important asset," he said, adding that a hotline would be set up where players, coaches or anyone else could report attempts to fix matches.

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