Their contest for football's top job turned increasingly hostile the day after bin Hammam was accused by the governing body of bribing voters in the Caribbean.
The Qatari challenger flew to Zurich for a FIFA finance meeting and faced the opponent he suspects plotted to wreck his chances in Wednesday's vote of 208 football nations. Their warm embrace, witnessed by a select few of FIFA's inner circle, disguised deeper passions.
Hours later, bin Hammam issued a statement urging the same FIFA ethics committee that is investigating him to also examine Blatter for breaching its behaviour code.
Blatter, meanwhile, talked up his opponent's "public humiliation" in his regular campaign column for a football website. He denied conspiring to remove his former ally from the ballot.
The dysfunctional spectacle finally prompted disapproval from a major sponsor that helps bankroll FIFA's billion-dollar annual income. The sporting goods firm Adidas, a top-tier backer since the 1970s, lamented the "negative tenor" of FIFA's debate.
Football's increasingly discredited ruling body already has eight of its 24-man executive committee under investigation. Blatter would be the ninth if, as bin Hammam requests, he is brought before an ethics hearing in Zurich on Sunday.
Bin Hammam has been summoned along with his fellow confederation boss Jack Warner, a FIFA vice president, for allegedly offering bribes to 25 Caribbean football leaders on a May 10-11 campaign trip to Warner's native Trinidad.
While rejecting the bribery allegations, bin Hammam said FIFA's evidence showed Blatter broke its ethical code by not reporting an apparent corruption attempt.
"The accusations also contain statements according to which Mr. Blatter, the incumbent FIFA president, was informed of, but did not oppose, payments allegedly made to members of the Caribbean Football Union," bin Hammam said in a statement.
Bin Hammam insisted the scandal is a "plan to damage" him and, like Warner, has questioned the timing.
Blatter wrote that he was "shocked" by the corruption claims against bin Hammam that shed a "very bad light on FIFA yet again."
"It gives me no pleasure to see him suffer public disgrace before an investigation would even have started," Blatter said in a column for Inside World Football. "To now assume that ... this entire matter was somehow masterminded by me is ludicrous and completely reprehensible."
The election rivals met briefly on Thursday - their first encounter since May 1 in Paraguay - in FIFA's main committee forum, according to senior vice president, Julio Grondona.
"They hugged in the room. There was no problem," the Argentine finance panel chairman said.
The ethics panel can, in effect, hand Blatter victory by suspending bin Hammam from all football duty. The panel could rule there was wrongdoing or it could provisionally bar bin Hammam if it requests more time to study evidence compiled by a federal prosecutor from Chicago who works for Warner's regional soccer body of CONCACAF, which represents North and Central America and the Caribbean.
Blatter expressed admiration for American official Chuck Blazer's "civic courage" in raising the alarm. Blazer joined the FIFA ruling panel alongside bin Hammam 15 years ago and had been Warner's closest regional ally for even longer.
The FIFA civil strife extended to CONCACAF's home city of New York. Manhattan lawyer Burton Haimes stepped aside from the FIFA ethics panel, citing a conflict of interest from his long-standing relationships with Blazer and Warner.
Ethics chairman Claudio Sulser recused himself on Wednesday because he shares Swiss nationality with Blatter. The former international player passed sentences last November on FIFA executive members Amos Adamu and Reynald Temarii. They drew three- and one-year bans respectively after an investigation into World Cup vote-selling. Sunday's hearing will be chaired by Sulser's deputy, Namibian judge Petrus Damaseb.
Blatter, who joined FIFA in 1975 and has been president for 13 years, acknowledges that FIFA helped create this stormy climate.
The 75-year-old Swiss pledged to "open the doors, reinforce dialogue, improve our corporate governance and handle our public affairs with the kind of priority it deserves" if he gets a fourth and final four-year term.
Adidas, which is in talks to extend its backing beyond the 2014 World Cup, appears to expect nothing less. It described FIFA's issues as "neither good for the sport of football nor for FIFA as an institution and its partners."
