(CNN) Amid calls for his dismissal Thursday, FIFA President Sepp Blatter blamed allegations of widespread corruption within soccer's governing body on "a few" and called for those involved to be punished as FIFA works to rebuild its reputation.

Blatter spoke at the opening of a FIFA World Congress that's expected to be like no other. Swiss authorities are investigating the 2018 and 2022 World Cup bids, while a U.S. investigation has led to the arrest of some of FIFA's leading officials on corruption charges, casting a shadow over the congress' 65th edition in Zurich, Switzerland, and a planned presidential election Friday.

"Let this be a turning point," Blatter said. "More needs to be done to make sure everyone in football acts responsibly and ethically."

He vowed to cooperate with authorities to ensure those involved in wrongdoing are "discovered and punished."

More bad news may arise and the coming months won't be easy, the longtime FIFA chief said, and he understands that many hold him responsible for FIFA's actions despite that he "cannot monitor everyone all of the time."

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"If people want to do wrong, they will also try to hide it, but it must fall to me to (be responsible) for the reputation and well-being of our organization and to find a way forward to fix things," he said.

The World Congress has an opportunity beginning Friday to start down "the long and difficult road to rebuilding trust."

"We cannot allow the reputation of football and FIFA to be dragged through the mud any longer. It has to stop here and now," he said. "You will agree with me these are unprecedented and difficult times for FIFA. ... Actions of individuals, if proven, bring shame and humiliation on football and demand action and change from us all."

Calls to step down

The 79-year-old's call for reform comes as a chorus of pundits, world leaders and European soccer's most important official have made clear what action they believe is necessary to clean up FIFA: Blatter must go.

On the eve of a vote that could put the embattled leader of soccer's scandal-ridden governing body into power for a fifth term, British Prime Minister David Cameron, much as expected, announced he will be supporting Jordan's Prince Ali Bin Al Hussein, the candidate put forth by England's Football Association to challenge Blatter's 17-year reign over world soccer.

"I fully support the Football Association's position that significant and wide-ranging reforms are urgently needed at the very top of FIFA, including a change in its leadership," he said, according to a statement.

And while a British Prime Minister's call for ouster may sound like it carries a lot of weight, we're talking about FIFA, an autonomous body that has survived numerous corruption scandals and defiantly stood firm in the face of widespread criticism of its decisions to hand Russia and Qatar the 2018 and 2022 World Cups.

But the words of Michel Platini likely will resonate. As president of UEFA, European soccer's governing body, he holds sway over votes that could threaten Blatter's grip on power.

Could Europe unseat Blatter?

Platini, who has been one of Blatter's critics, met with other UEFA officials in Zurich on Thursday to decide how best to navigate the growing scandal.

Following that meeting, the former French national player told reporters that he had asked Blatter to leave, and Blatter was "very sensitive on that," but told Platini it was "too late," given that the vote is set for Friday.

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Platini said he knows Blatter's strategy. "His strategy is to bring all the congresses, to have some speakers in the room, to convince ... the most to vote for him, and then at the end he will say, 'Look at the democracy. Democracy of the most numbers, they will say that I have to stay. And I will stay.' "

Platini said he spoke to Blatter as a friend -- "He always says that he was an uncle for me." Pressed on why he asked Blatter to step down, he replied, "I think he's a friend who has a problem and he's not good for the rest. It is my duty to tell that."

As for the prospect that Prince Ali could unseat Blatter, Europe could bring as many as 54 votes for the contender -- and a minimum or 45 or 46, "if I trust everybody," Platini said with a chuckle.

He'll also have the support of the United States, said Sunil Gulati, the head of the U.S. Soccer Federation.

Each of FIFA's 209 member associations has a vote. A candidate needs two-thirds of the first ballot to be president if all members vote. Blatter secured his 2011 re-election with 186 votes in his favor, out of 203. If there is no winner after the first vote, members cast ballots again, with only a majority of 105 needed to win.

The Asian Football Confederation took the opposite tack, announcing Thursday that while it was disappointed by reports of corruption, it was ready to stand by Blatter and was against delaying the presidential elections. The Asian Football Confederation has 46 voting members.

The Confederation of African Football said the same in a statement Thursday. The CAF has 54 votes, and as recently as last month had promised to support Blatter unanimously.

If Blatter is re-elected, Platini said, European nations could take action of their own.

"Many people, they don't want to stay with this FIFA, and if Sepp is still the president, UEFA has to take its responsibility," he said.

Will vote be postponed?

Thursday, Blatter held an emergency meeting with representatives of its six confederations before the opening of the congress.

Already, there have have been calls for the FIFA presidential ballot to be postponed.

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UEFA said Wednesday its member associations should consider whether to attend the upcoming FIFA World Congress, which it said should be postponed. UEFA further called for "new FIFA presidential elections to be organized within the next six months."

Nine FIFA officials, as well as five sports media and marketing executives, were charged by U.S. prosecutors Wednesday over alleged kickbacks of more than $150 million dating back over 20 years.

As a result of the U.S. investigation, seven arrests were made in a dawn raid of a Zurich hotel where the officials had gathered for the annual congress.

Among those arrested was Jeffrey Webb, a FIFA vice president and head of CONCACAF, who FIFA banned Wednesday from "football-related activities" as a result of the investigation. CONCACAF announced Thursday it had provisionally dismissed Webb.

In a separate development, Swiss authorities announced an investigation into the award of the 2018 and 2022 World Cups to Russia and Qatar.

Blatter has not been named as a suspect in either investigation, but doubts about his leadership of world soccer have again resurfaced, not least because key FIFA sponsors Visa and Coca-Cola have put out statements expressing their concerns about its handling of persistent allegations of corruption.

Andre Marty, the spokesman for the Swiss attorney general's office, said Thursday investigators "won't hesitate to question the FIFA president if need be."