By Marcus Leach
Following allegations that Fifa president Sepp Blatter knew about alleged cash payments the football governing body has opened ethics proceedings against him.
Blatter's presidency rival, Mohamed Bin Hammam, made the claims ahead of next week's election.
Blatter will not be the only one at Sunday's hearing, as Bin Hammam and vice-president Jack Warner are set to answer charges of bribery.
"I cannot comment on the proceedings that have been opened against me. The facts will speak for themselves," Blatter said in a statement.
Article 16 of the ethics code states that the ethics committee are bound by their rules to investigate any complaint levelled by an executive committee member.
The investigation into Bin Hammam and Warner relates to the allegations, made by executive member Chuck Blazer, that the pair offered bribes at a meeting of the Caribbean Football Union (CFU) on 10 and 11 May.
Blazer's alleges that bundles of cash, up to a value of $40,000, were given to certain members of the CFU at a meeting in Thailand. This in turn sparked Bin Hammam to claim Blatter was well aware of the wrongdoing, but failed to report it and thus breaching the code.
The committee will be chaired by Namibian judge Petrus Damaseb, who will come under intense pressure to decide if charges are to be brough against Blatter.
That Blatter, regarded as one of the most powerful men in world football, has been placed under investigation is just another twist in what is turning into a bitter struggle for the presidency of Fifa.
What is worse for Fifa is that it comes just weeks after the media storm concerning the vote for the 2018 and 2022 World Cups had died down.
"Fifa is now an organisation completely at war. They cannot possibly continue in this way and many people will say they should suspend the presidential election, which takes place next Wednesday," BBC sports editor David Bond said.
"Under Fifa's ethics code, they are duty bound, if a member of the executive committee makes a complaint to the ethics committee, to then investigate it.
"So, it may be that the allegations against Blatter don't come to much, and the allegations against Bin Hammam and Warner could be far more serious. Ultimately it seems the evidence against Blatter is only Bin Hammam's word against his.
"It is very difficult to predict exactly what will happen next, but it's hard to see this as anything other than a watershed moment for Fifa.
"It feels like at last the dam is breaking around them. It is a bit like the scene at the end of Reservoir Dogs when everyone has a gun pointed at each other's heads."