Image copyright Getty Images Image caption England play Costa Rica in Brazil during the 2014 World Cup, of which Visa is a main sponsor

Fifa has admitted the corruption scandal is putting off new World Cup sponsors and plans to hold a summit with existing backers in August.

Secretary-general Jerome Valcke said: "The current situation doesn't help to finalise any new agreements."

Earlier, key sponsor Visa lambasted Fifa for a "lack of awareness" of the seriousness of corruption charges.

This week, Fifa said it would set up an 11-strong taskforce to examine the issue of corruption.

The August meeting was first suggested by major sponsors, Mr Valcke said.

"Clearly, there were a number of sponsors, mainly three, Coca-Cola, McDonald's and Visa, who... sent a letter to Fifa, asking for information," he said.

"Two or three days ago we received a letter from all of them offering to meet together, so there will there will be a meeting next month."

Visa chief executive Charlie Scharf on Thursday expressed his concern over the situation, telling investors his payments company sought partnerships with those "who think and act like us".

He said it tried to hold the highest standards, but did not believe Fifa was living up to those.

Fraud

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Visa has been one of the most critical of Fifa's top sponsors. Nevertheless, such public plain talking is rare.

Coca-Cola and McDonald's have also been vocal about their concerns.

Fifa's other key sponsors include Budweiser and Adidas.

Top Fifa officials were arrested earlier this year on charges of racketeering, wire fraud and money laundering as part of a US prosecution that also indicted 14 people.

It sparked the resignation of its president, Sepp Blatter, who announced he intended to leave next year.

'Crisis'

Mr Scharf expressed a lack of confidence in Fifa's ability to reform, saying "no meaningful reform can be achieved under the current leadership", although he stopped short of asking anyone to resign.

He is calling for an independent commission to be set up to plan for reform. Eleven days ago Coca-Cola also called for such a body to be set up.

Lobby groups backed Mr Scharf's comments.

Transparency International (TI), NewFIFANow and the International Trade Union Confederation all applauded Visa for its stance.

"Coca Cola and Visa have rightly recognised the depth of the corruption crisis facing Fifa," said TI's Neil Martinson.

Mr Scharf's full remarks are: "We view the stewardship of our company, our brand, and our clients with the utmost importance and try to hold ourselves to the highest standards.

"We seek to partner with those who think and act like us. I don't believe that Fifa is living up to these standards. Furthermore, their subsequent responses are wholly inadequate and continue to show its lack of awareness of the seriousness of the changes which are needed.

"To this end, we believe two things need to happen to ensure credible reform. First, an independent, third-party commission led by one or more impartial leaders is critical to formulate reforms. Second, we believe no meaningful reform can be made under Fifa's existing leadership.

"Football itself is a great sport with which we are proud to be associated. We want to be proud to be associated with Fifa and hope and look forward to working with them to that end."

Who are Fifa's five top tier partners and two World Cup sponsors?

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Adidas - the German sportswear firm has been supplying the official match ball for all Fifa World Cup tournament matches since 1970. Also involved in all other Fifa events, such as the Confederations Cup Brazil 2013, and the Fifa U-20 World Cups for women and men.

Coca-Cola - the US soft drinks firm is one of the longest-standing corporate partners of Fifa, with a formal association since 1974 and an official sponsorship of the Fifa World Cup that began in 1978. Coca-Cola has had stadium advertising at every Fifa World Cup since 1950.

Gazprom - the Russian energy giant signed up with Fifa in 2013 as a partner for all competitions in the period of 2015 to 2018, including the 2018 Fifa World Cup, which is due to take place in Russia for the first time. (The firm is also an official partner of the Uefa Champions League 2012 to 2015).

Hyundai/Kia - the South Korean carmaker began its Fifa alliance in 1999, in a deal to sponsor 13 Fifa competitions including the 2002 World Cup. That agreement was extended to the 2006 event. It again backed the 2010 World Cup and is now the official automotive partner of Fifa until 2022.

Visa - the credit card company became a top-tier Fifa partner in 2007, taking over from rivals MasterCard in controversial circumstances, and recently extended its relationship until 2022. It is a sponsor of five Fifa events this year, including the Women's World Cup in Canada.

Budweiser - the US beverage has been a World Cup sponsor since the 1986 event in Mexico, and is the official beer of the tournament, with its product on sale in all stadia at the finals. The brand also sponsors the man of the match award at each game.

McDonald's - the fast food chain has been a sponsor since the 1994 World Cup in the US. Its products are available at all matches in the finals tournament, and it also sponsors the World Cup player escort programme, in which children accompany the teams onto the pitch.