• Kia and Gazprom also silent on issue of Fifa president • UK sports minister calls on Blatter to go as soon as possible

Adidas, Fifa’s oldest sponsor, and the South Korea car company Kia have declined so far to join four other major backers in pressuring the president, Sepp Blatter, to resign immediately.

In an apparently co-ordinated move the United States giants Coca Cola, Visa, McDonald’s and Budweiser all said on Friday night that Blatter’s continued presence as Fifa president was holding back reform efforts and called on him to go amid a spiralling corruption crisis.

The four US companies have been under pressure to act since the US Department of Justice charged 14 people, including nine current or former Fifa executives, in May with crimes involving racketeering, fraud and money laundering.

But Adidas, the German sportswear firm that has supplied the ball for every World Cup since 1970 and has a contract that runs until 2030, on Saturday declined to follow its fellow sponsors in calling for Blatter to go immediately rather than limping on until February.

A spokesman told the Observer: “As pointed out several times already, Fifa must implement fundamental changes for the sake of football. Therefore, the initiated reform process must continue quickly and transparently.”

The histories of Adidas and Fifa are closely entwined. It was Horst Dassler, the son of the company’s founder, who helped lever Blatter into power as general secretary and in 1982 co-founded International Sport and Leisure. The sports marketing company became Fifa’s main partner for broadcasting rights but, following Dassler’s death, went bankrupt and was involved in allegations surrounding a $100m (£65.8m) kickback scheme in which money was diverted to Fifa executive committee members.

Fifa’s two other main sponsors, Kia and Gazprom, were the only ones who did not attend a summit meeting called by the Fifa secretary general, Jérôme Valcke, in the wake of May’s arrests to try and allay the concerns of sponsors as the organisation went into meltdown.

Valcke himself has since been suspended by Fifa’s ethics committee while it investigates claims that World Cup tickets were sold above face value with his knowledge. He denies the allegations.

The four US companies, who between them contribute a large proportion of the £1.1bn that Fifa earns every four years from World Cup sponsors, all issued similar statements in which they urged Blatter to step down now and called for independent reform.

Coca-Cola’s intervention is seen as particularly crucial as, like Adidas, it was in on the ground floor of the global sports marketing model that has led to huge global growth for Fifa and its sponsors.

Given that Fifa’s main sponsors contribute $1.6bn towards its $5.7bn revenues over each four-year cycle and their brands are at risk when tainted by corruption allegations, a rebellion by sponsors has long been seen as one of the most likely levers for change.

Campaigners have previously been frustrated by the firms’ refusal to push for a systemic overhaul of Fifa but May’s arrests followed by last week’s dramatic move by the Swiss attorney general to open criminal proceedings against Blatter appears to have been a tipping point.

In June, the Guardian revealed that Coca-Cola, McDonald’s and Visa had called for an independent, external reform process.

Blatter, who claims to have done nothing wrong and insists he will stay on until February, was accused of selling TV rights to the disgraced former Fifa vice president Jack Warner at below market value and of making a “disloyal payment” of £1.3m to the Uefa president, Michel Platini.

Platini,who like Blatter is under investigation by Fifa’s ethics committee, was questioned by the Swiss authorities as a person “somewhere between a witness and an accused person”.

But he insists he has done nothing improper and still plans to stand in February’s election to replace Blatter. He has now called on the French sports ministry to reiterate his innocence.

“He has the feeling he is clean and he wanted to say it to me again,” the secretary of state, Thierry Braillard, told the French sports daily L’Equipe on Saturday. “He explained everything. I fully trust his honesty and his determination to become Fifa president,” he added.

The French sports minister Patrick Kanner also gave his support to Platini on Saturday. “We have not changed our minds on the support we give him. If there was any problem, I do not doubt for a minute that he would have refused to run for Fifa president,” he told L’Equipe.

“His message to us was ’continue to trust me’. That’s what he wanted to tell us.”

Platini claims that he had a contract as Blatter’s adviser between 1998 and 2002 but was not paid in full as Fifa could not afford it – despite the fact it posted a 155m Swiss franc surplus during the period in question.

The outstanding £1.3m was eventually paid in February 2011, two months before Blatter was re-elected and two months after Qatar won the controversial 2022 World Cup vote.

After FA chairman Greg Dyke declared that the intervention of the sponsors was a “game changer”, on Saturday the UK government added its voice to calls for Blatter to stand down immediately. Sports Minister Tracey Crouch said: “The sooner Blatter goes, the sooner wide-scale reform at Fifa can begin.”