ST PETERSBURG, Russia — It is the moment every politician dreads: the private conversation caught by the open microphone.

A chat between President Bush and Prime Minister Blair was recorded at yesterday’s closing lunch at the G-8 summit. As he munched on a bread roll, Mr. Bush said: “The irony is, what they need to do is get Syria to get Hezbollah to stop doing this sh—, and it’s over.” It is unclear who “they” are.

Potentially far more embarrassing for Downing Street was the exchange over the possibility of a trip by Secretary of State Rice to the Middle East.

Mr. Blair made it clear he would be delighted to go instead of Ms. Rice or to pave the way for her on the grounds, apparently, that he is such a weakened leader that it would not matter if his trip failed.

“She’s going. I think Condi’s going to go pretty soon,” the president said after Mr. Blair pressed him on the need for someone to get the “lie of the land.” “I told her your offer, too,” Mr. Bush added in a reference to an apparent earlier offer by the prime minister to visit the region.

“It’s only if she needs the ground prepared, as it were,” Mr. Blair said. “Obviously if she goes out she’s got to succeed, as it were, whereas I can just go out and talk.”

The recording will be seized on eagerly by the British leaders’ critics, who have long argued that Mr. Blair is overly keen to please Washington and that Mr. Bush sees the world in rather simple terms.

The leaders also appeared unconvinced by the approach of the U.N. secretary-general. “What about Kofi Annan? I don’t like the sequence of it,” the president said. “His attitude is basically cease-fire and everything else happens.”

“What does he think?” Mr. Blair said. “He thinks if Lebanon turns out fine, if he gets a solution in Israel and Palestine, Iraq goes in the right way, he’s done it. That’s what this whole thing’s about. It’s the same with Iran.”

Mr. Bush displayed his trademark informality, joking with leaders about their journey home. “Yeah, Blair, what are you doing?” he said at one point. “You leaving?”

“You get home in eight hours?” he says to another leader. “Me, too! Russia’s a big country and you’re a big country. Gotta go home. Got something to do tonight.”

“Thanks for the sweater,” he said of his 60th birthday present from the prime minister. “Awfully thoughtful of you. I know you picked it out yourself.”

Mr. Bush over the years has been careful to avoid being overheard swearing. The last time he was caught out in such a way was six years ago, before he was in the White House, when he was overheard describing a New York Times correspondent as a “major league —hole.”

He may not be too concerned at this latest slip, given that the target of his abuse was Hezbollah. When Vice President Cheney used far stronger language in 2004, telling a Democratic congressman to leave him alone, opinion polls suggested many on the Christian right approved.

The recording also picked up Mr. Bush speaking to other leaders, bantering about his preference for Diet Coke, and making clear his irritation at the formalities of summitry.

The thought of making an after-lunch farewell toast clearly did not appeal — nor did the prospect of listening to fellow leaders, some of whom he clearly thinks are far too in love with the sound of their own voices. “I’m just going to make it up. I’m not going to talk too damn long like the rest of them. Some of these guys talk too long.”