(CNN) -- Journalists covering last week's economic summit overheard French President Nicolas Sarkozy blasting Israeli Prime Minister Benjamin Netanyahu as a "liar" during a talk with U.S. President Barack Obama, according to published reports.
The private conversation was inadvertently carried by open microphones before an Obama-Sarkozy news conference on the sidelines of the Group of 20 economic summit in the French resort of Cannes. Its contents were first reported by the French website Arret Sur Images, which said reporters heard Sarkozy's comments in French and Obama's reply through a translator.
"I can't stand him. He's a liar," Sarkozy said of Netanyahu, according to the website.
Obama replied, "You're tired of him; what about me? I have to deal with him every day," the site reported.
Arret Sur Images ("Freeze Frame") said journalists had listened in on the conversation but had agreed not to report it. The Reuters and Associated Press news services confirmed that report Tuesday.
"We didn't record it, and to use it would force us to admit that we had cheated," Arret Sur Images quoted one of the reporters who heard the conversation, whom it did not name. "Also, it would have caused great problems for the people responsible for the event's organization."
Dan Israel, the Arret Sur Images writer who broke the story, told CNN that about three minutes of the leaders' private conversation could be heard.
"It was a mistake by the organization for the G-20 summit," Israel said. He said journalists agreed among themselves to consider the remarks off the record because they didn't want to get a summit staffer heard into a "rough patch" after he disclosed that the audio could be heard. But the word spread rapidly among journalists in Paris, prompting Arret Sur Images to start chasing the report, he said.
"Some of them did give me the quotes, and others just confirmed the quotes," Israel said.
The report was met with silence from the Elysee Palace, the French president's office, which did not respond to requests for comment.
In Washington, White House spokesman Jay Carney said he had no comment on the conversation or Obama's response but said, "The president's position has been quite clear on the issue of efforts by the Palestinians to achieve through the U.N. what can only be achieved effectively through direct negotiations."
Netanyahu's office also had no comment. But in the United States, the Anti-Defamation League said it was "deeply disappointed and saddened" by the private conversation, warning that it could hurt ties between Israel and two key players in the Middle East peace process.
"President Obama's response to Mr. Sarkozy implies that he agrees with the French leader," ADL Director Abe Foxman said in a written statement. "In light of the revelations here, we hope that the Obama administration will do everything it can to reassure Israel that the relationship remains on a sure footing and to reinvigorate the trust between President Obama and Prime Minister Netanyahu, which clearly is not what it should be."
A member of Netanyahu's coalition in the Knesset, Israel's parliament, said "there is not much love lost" between the Israeli leader and his counterparts.
"It's unpleasant," said Einat Wilf, whose Independence party is allied with Netanyahu's ruling Likud. "Of course, we would all like to be loved and all love to have great relationships with each other, and I'm sure it would be nicer to know that our prime minister is loved. But at the end of the day, what did Machiavelli say? It's more important to be feared than loved."
Israeli opposition leaders have questioned Netanyahu's honesty before, but Labor Party lawmaker Daniel Ben-Simon said he was "ashamed" that the leaders of two of Israel's top allies "could characterize my prime minister as a liar."
"If the most friendly leaders say that about my prime minister, what do others say about him who are not as friendly?" said Ben-Simon, the head of the Israeli-French Parliamentary Association."If he lies to them, he must be lying to Israelis as well."
CNN's Alexander Mooney, Kevin Flower and Alanne Orjoux contributed to this report.