"I cannot stand him [Netanyahu]. He is a liar," Sarkozy told U.S. President Barack Obama when the two met after conducting a press conference at the Group of 20 summit in Cannes last Thursday, the French Web site Arretsurimages.net reported.
Obama allegedly responded, telling Sarkozy, "You're fed up with him, but I have to deal with him every day," the French Web site said.
White House spokesman Jay Carney refused to comment on the substance of the alleged remarks at the daily press briefing in Washington, saying only U.S.-French differences on handling the Palestinian issue are well known.
The meeting began with Obama criticizing Sarkozy for failing to warn him France planned to vote in favor of the Palestinians seeking membership at UNESCO, despite U.S. objections.
The two were unaware microphones in the room had been left on and every word over a period of three minutes was heard before the authorities shut the microphones down.
At least six journalists who had headsets for translation purposes heard the remarks but were bound by an agreement they signed prior to the summit not to publish them, the site said.
Arretsurimages.net said it was not bound by the agreement and got confirmation from some journalists who were present.
"To our knowledge, these explosive statements, their existence or the contents have been confirmed by several journalists, were not published (but they were mentioned in one sentence on the blog Arnaud Leparmentier, du Monde)," the site said.