The battle for FIFA's top job was thrown into further turmoil on Sunday when president Sepp Blatter's main rival for the post, Mohamed bin Hammam, ended his campaign amid a bitter fall-out over allegations of corruption.

Bin Hammam's decision came just hours before both the Qatari and Blatter were scheduled to face the ethics committee of soccer's world governing body over bribery allegations.

As Blatter was due to respond to claims that he knew about cash payments at the centre of a probe targeting bin Hammam, the latter ended his campaign saying he was "hurt and disappointed".

"It saddens me that standing up for the causes that I believed in has come at a great price - the degradation of FIFA's reputation," said 61-year-old bin Hammam (pictured), who campaigned on an anti-corruption platform and had waged a bitter war of words with long-serving Blatter.

Bin Hammam had demanded the corruption investigation be widened to include Blatter on Thursday as the two men prepared to contest a June 1 election for control of FIFA.

Two days earlier, bin Hammam, FIFA vice-president Jack Warner and two Caribbean Football Union officials had been summoned to the ethics committee to answer corruption allegations.

Bin Hammam and Warner were targeted after Chuck Blazer, general secretary of regional football body CONCACAF, reported possible misdeeds during a May 10 and 11 meeting in Trinidad.

British media reports said bin Hammam and Warner are accused of offering $40,000 in cash gifts to national associations at the Trinidad conference in return for their votes in next week's presidential election.

A FIFA statement on Friday said Blatter, 75, had been summoned to appear before the ethics committee to answer claims that Warner had told him in advance of alleged payments made at the meeting.

Blatter issued a brief statement on Friday following FIFA's announcement, saying: "The facts will speak for themselves."

Blatter has denied suggestions from bin Hammam that he orchestrated the charges against the man seeking to unseat him, dismissing them as "ludicrous".

Writing on his blog on Saturday, bin Hammam vowed to clear his name of "baseless allegations".