Their contest for control of world football's top job turned increasingly hostile the day after bin Hammam was accused by FIFA of bribing voters in the Caribbean.
The Qatari challenger flew into Zurich for a scheduled FIFA finance meeting, and faced the election foe he suspects plotted to wreck his chances in a poll of up to 208 football nations scheduled next Wednesday.
Their warm embrace, witnessed by a select few of FIFA's inner circle, disguised deeper passions.
Hours later, bin Hammam issued a statement urging FIFA's ethics committee which is investigating him to also examine Blatter for breaching its behavior code.
Meanwhile, Blatter talked up his opponent's ''public humiliation'' in his regular campaign column for a football website, and denied conspiring to remove his former ally from the ballot.
The dysfunctional spectacle finally prompted disapproval from a major sponsor which helps bankroll FIFA's billion-dollar annual income.
Sports goods firm Adidas, a top-tier backer since the 1970s, lamented ''the negative tenor'' of FIFA's debate.
Football's increasingly discredited governing body already has eight of its 24-man executive committee currently under investigation.
Blatter would be a 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 that 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 which 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 effectively hand Blatter victory by suspending bin Hammam from all football duty. The panel could rule that wrongdoing was proven, 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 North, Central American and Caribbean (CONCACAF) regional body.
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 which will be settled in Zurich stretched across 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 who got three- and one-year bans respectively after a probe 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, accepted FIFA helped create the current 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.''