FIFA President Sepp Blatter announced he will resign after the organization elects a new leader at an “extraordinary congress.” His surprise resignation comes days after his reelection. (YouTube/FIFATV)

Sepp Blatter, the longtime president of FIFA, announced his resignation Tuesday, a stunning about-face that came just days after he celebrated his reelection and defiantly criticized U.S. law enforcement agencies leading a corruption investigation that has rocked world soccer’s governing body.

While it remains unclear what prompted Blatter’s resignation, two people familiar with the case said Tuesday that Blatter remains a focus of the sprawling investigation into FIFA and that federal prosecutors hope to get evidence from those already arrested to secure further indictments. No new charges were announced Tuesday.

In a short news conference at FIFA’s Zurich headquarters, Blatter admitted no wrongdoing but acknowledged that he had lost the support of “the entire world of football” and called for an election to select his successor. Blatter will remain president until a new election, and no date has been set. Until he steps down, Blatter said, he will focus on imposing “far-reaching, fundamental reforms” in the organization that oversees the world’s most popular sport.

“I cherish FIFA more than anything, and I want to do only what is best for FIFA and for football,” said Blatter, 79, who has served as FIFA president since 1998. “FIFA needs a profound overhaul.”

The admission of a need for massive change — including term limits for leadership and an overhaul of the powerful executive committee — represented a startling reversal for Blatter, who Friday told the assembled delegates of FIFA’s member nations that “we don’t need revolutions; we just need evolutions.”

Sepp Blatter has won a fifth FIFA presidential term after his only challenger conceded defeat in an election overshadowed by allegations of corruption among some of its top overseers. (Reuters)

A years-long U.S. criminal inquiry into FIFA erupted into public view last Wednesday. In Zurich, Swiss authorities arrested several FIFA officials, including two vice presidents, in a dramatic early morning raid at a five-star hotel. Hours later, American law enforcement agencies unsealed a 47-count indictment that named 14 officials at FIFA and global sports marketing companies in a number of schemes involving bribery, fraud and money laundering. FIFA officials took bribes from countries bidding to host the World Cup, the indictment asserted, and from companies vying for lucrative media deals associated with other soccer tournaments.

While Blatter initially said he welcomed the U.S. investigation, after his reelection he seemed less appreciative. In interviews over the weekend, Blatter said “there is something that smells” about the timing of indictments two days before FIFA’s presidential election. Blatter said American law enforcement had overstepped by making arrests on foreign soil, and he criticized comments by Attorney General Loretta E. Lynch, who described corruption in FIFA as “rampant, systemic, and deep-rooted.”

Those interviews made Tuesday’s turn all the more stunning. While Blatter has not been charged with a crime, federal authorities believe his top lieutenant, FIFA secretary general Jérôme Valcke, was involved with the transfer of $10 million from FIFA to accounts controlled by another FIFA official in 2008, according to a person briefed on the case. That money was part of a bribe paid by South African officials to secure the 2010 World Cup, law enforcement documents state.

Valcke’s possible involvement was first reported Monday evening by the New York Times, which noted that he might not have known the money was part of a bribe. South African officials have denied paying bribes to land the World Cup. Valcke has not been charged with a crime.

Tuesday’s announcement means the beginning of the end of a long career for Blatter, a Switzerland native who worked in public relations for the Swiss Ice Hockey Federation and for a watch manufacturer before joining FIFA in 1975. In 1981, he was appointed FIFA general secretary, and for years before he ascended to the presidency, Blatter played a leading role negotiating the lucrative television rights associated with the World Cup, which provides much of FIFA’s revenue.

While Blatter proved adept at increasing FIFA’s wealth, the organization he ran has been plagued by rumors of corruption, bribes and backroom deals, usually involving its presidential elections and its votes on World Cup sites. Blatter’s resignation immediately calls into question whether the 2022 World Cup will go on as planned in Qatar, whose winning bid might be the most controversial in FIFA’s history.

Blatter’s announcement was welcomed by government officials, players, and commentators across Europe and the Americas. U.S. Soccer President Sunil Gulati called it “an exceptional and immediate opportunity for positive change within FIFA.”

“Today is an occasion for optimism and belief for everyone who shares a passion for our game,” Gulati said.

Latin American news Web sites were running banner headlines of the news, and much of the tone was exultant, as players and officials celebrated his departure and expressed hope of cleaning up the sport.

Brazilian soccer legend and current senator Romario de Souza Faria, known simply as Romario, wrote on Facebook that Blatter’s resignation was the “best news in ages” and that it “begins a new era for world football.”

Argentine soccer god Diego Maradona told an Argentine radio station that “today the truth is out and I am enjoying it.”

“They hate soccer,” Maradona said of FIFA officials. “They hate transparency. Enough shady dealings. Enough lying to the people.”

Wilmar Valdez, the vice president of Conmebol, the South American soccer confederation, expressed surprise over the resignation. “Something had to have happened for him to make this decision,” he was quoted as saying.

Britain’s sports and culture secretary, John Whittingdale, called Blatter’s move “belated” and said it was “only the beginning of the process of change we need to see from FIFA.”

Also happy to see Blatter go was Greg Dyke, chairman of England’s Football Association, and a persistent Blatter critic.

“He’s stood down. He’s gone. Let’s celebrate,” Dyke told the British Broadcasting Corp. “This is nothing to do with Mr. Blatter being honorable. He hasn’t been honorable in years.”

Others cautioned that Blatter’s decision to resign was just the first step in rehabilitating soccer’s image. Vincent Kompany, captain of the Manchester City soccer club, wrote on Twitter that Blatter wasn’t the only one responsible for the sport’s den-of-thieves reputation. Soccer, Kompany wrote, still needs “transparency and voting reform, then we move on and bring back ethics.”

In Germany, home of the reigning World Cup champions, the news of Blatter’s resignation was met with relief, even ecstasy. His rule was long seen as a thorn in the eye of soccer, with street graffiti in Berlin even likening FIFA to the mafia.

Hans Sarpei, German-Ghanaian former professional soccer player, tweeted: “I’ll go to my office now and dance with joy.”

Arne Friedrich, a former player on Germany’s national soccer team tweeted, in English: “Sepp Blatter resigned. At least one good news around the #FIFA scandals. Will be exciting what else is going to come up shortly.”

German soccer legend Franz Beckenbauer told German tabloid Bild: “It was a reasonable decision by Sepp Blatter. The pressure was getting too high. He would never have had his peace, no matter whether the scandals are his fault or not. Fifa’s problem lies in its system.”

“This is the absolutely right decision, and it is overdue,” Wolfgang Niersbach, the president of the German Football Association, told German media. “It is a tragedy actually, that he did not spare himself and all of us by doing this earlier.”

Griff Witte in London, Anthony Faiola and Stephanie Kirchner in Berlin, and Joshua Partlow in Mexico City and Rosalind Helderman in Washington contributed to this report.