FIFA members on Friday started a congress to choose a new president in place of Sepp Blatter to lead world football away from scandal amid warnings that its reforms must be credible.

The landmark presidential contest is an Asia v Europe battle between Sheikh Salman bin Ebrahim Al Khalifa and Gianni Infantino.

But former FIFA vice-president Prince Ali bin al Hussein is aiming to upset the odds and he received a boost with the heavyweight backing of the United States and Australia.

Outsiders Jerome Champagne, an ex-FIFA official, and South African tycoon Tokyo Sexwale, have also been doggedly pleading their cause to the more than 200 delegations in Zurich.

The result is uncertain but football leaders were given an immediate warning that the vote and new reforms must convince the world after several years of mounting scandal with corruption and doubts about World Cup bidding.

"This congress will quite certainly mark a watershed moment in the history of FIFA," acting FIFA president Issa Hayatou said in his opening speech.

The scandal of the past year "shook the very foundations of our organisation."

International Olympic Committee president Thomas Bach said that football and all sports federations had to improve governance.

"Today you have this great chance to turn the page," he said.

"We need to give new answers to the new questions with regards to credibility and good governance," he said.

Blatter, 79, will be the big absentee at the extraordinary congress. The Swiss sports baron suffered a spectacular fall over the last nine months.

Swiss police, acting under US warrants, arrested seven FIFA officials in Zurich two days before his re-election last May.

Blatter has since been banned from football for six years for ethics breaches and could face criminal charges.

Infantino, general secretary of Europe's football bloc UEFA, and Sheikh Salman, president of the Asian Football Confederation, have offered starkly different paths for FIFA.

While promising reforms similar to those to be voted Friday, Infantino has proposed increasing the World Cup from 32 to 40 teams and to more than double the amount given back to the 209 national associations to more than $1 billion in total every four years.

Sheikh Salman, who is seen as closer to the FIFA old guard and has a bedrock of support in Asia and Africa, has said the proposal could bankrupt FIFA.

He said Thursday he would not "mortgage" FIFA's future to win votes.

The sheikh has advocated splitting FIFA into commercial and football divisions with himself as more of a figurehead president.

Each of the rivals has political problems.

Infantino was for seven years the right-hand man of Michel Platini, the UEFA president also banned for six years for ethics breaches.

Sheikh Salman, a senior member of Bahrain's ruling family, has faced tough questions about the clampdown on pro-democracy protests in the Gulf state. He has called allegations made by human rights groups "nasty lies."

Going into the election, the voting maths is dizzying for Infantino and Sheikh Salman. Both have expressed confidence, however.

The AFC and Confederation of African Football (CAF), which between them have 100 votes, have publicly said they are backing 50-year-old Sheikh Salman.

However, Football Federation Australia, a member of the AFC, said Friday it will vote for Prince Ali, who also received the backing of the United States.

Europe and a big bloc of votes in the Americas are largely behind 45-year-old Infantino, who was publicly endorsed by Canada on Friday.

Prince Ali, a brother of Jordan's King Abdullah II, believes he has persuaded a significant number of countries to back him.

The election, the prince said "will decide if FIFA goes ahead as we want or if it spirals down."

The congress is also to vote on reforms proposed by a FIFA commission and backed by the body's executive committee aiming to re-establish its credibility.

There will be a 12-year term limit for the president and other top officials, and their salaries will be made public.

Executive committee members will also face greater scrutiny. Many of the 39 individuals now accused by US prosecutors of involvement in more than $200 million of bribes for soccer deals have held high office on the committee.

"The eyes of the world are on us," Hayatou said, as he urged member nations to back the reforms.

FIFA's sponsors who are holding out on deals and prosecutors in many countries will be watching the result for signs of football's commitment to reform.

The sport's top leagues also want to see a revolution.

"If FIFA and the people in FIFA are not going to act on the message from the whole world that it is time to change... then the system fails," Jacco Swart, head of the Dutch Eredivisie professional league, told AFP after a briefing of the newly created World Leagues Forum.