Shaul Mofaz, the opposition leader in the Israeli Parliament, attacked Mr. Netanyahu, accusing him of breaking a cardinal rule by meddling in American politics.

“Prime Minister, who do you think is Israel’s greatest enemy? The United States or Iran?” he asked from the lectern in Parliament. “Who do you fear more, Mr. Netanyahu — Ahmadinejad or President Obama?” he said, referring to the Iranian president.

“Which administration is it more important for you to replace — the administration in Washington or that in Tehran?” he added. “Explain to us, Mr. Prime Minister, what are your red lines in managing the current crisis with the Americans over Iran?

Mr. Netanyahu had said Tuesday that “those in the international community who refuse to put red lines before Iran don’t have a moral right to place a red light before Israel.” He was apparently responding to a weekend statement by Secretary of State Hillary Rodham Clinton that the United States was “not setting deadlines” beyond which it would turn to a military solution. The verbal tit for tat capped months of public sparring by senior Israeli and American officials.

“Both sides have said things that, in my humble opinion, should not have been said,” said Sallai Meridor, who was Israel’s ambassador to the United States from 2006 to 2009.

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With the Iranians listening to every word, he said, the open discussions and the casting of aspersions on each other’s will or capability to act are “a very unfortunate, if not dangerous, development.” He added, “If there’s a difference of opinion in the family, so to speak, you don’t go public.”

Mr. Netanyahu is perceived as trying to leverage the pre-election period to win more explicit American commitments on Iran, and some have interpreted his sharp criticism of Mr. Obama as open support for Mitt Romney.

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But many here, including some longstanding critics of Mr. Netanyahu, said they did not believe his remarks were motivated by politics.

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“I think he really believes a threat is looming,” said Isaac Herzog, a former cabinet minister and chairman of Parliament’s Labor Party faction, “and he wants to stop it.”

Several analysts and experts here attributed Mr. Netanyahu’s outburst to deep frustration with the United States for telling Israel to hold off on a military strike against Iran, and to a feeling in Israel that time is running out for any unilateral action.

“Netanyahu believes he needs some understanding with the United States, because he does not have enough support in Israel” to go it alone, said Eytan Gilboa, a professor at the Begin-Sadat Center for Strategic Studies at Bar-Ilan University.

Though the Iranians insist that their nuclear program is for peaceful purposes, Israel views a nuclear Iran as an existential threat and Mr. Netanyahu has frequently equated Iran with Nazi Germany and raised the specter of a second Holocaust.

“I think Netanyahu found himself in a place where he felt he had not much to lose,” said Avinoam Bar-Yosef, the president of the Jewish People Policy Planning Institute in Jerusalem. “He tried to see Obama, but Obama did not want to see him,” Mr. Bar-Yosef said, referring to Mr. Netanyahu’s failed attempt to secure a meeting with the president when he visits the United Nations this month.

Mr. Netanyahu’s relations with Mr. Obama may have been tense over the years, but given the close ties between Israel and the United States, few here think the relationship will be seriously damaged by one sharp statement.

But many cautioned against intervening in American politics. Israel sees the bipartisan support it has long enjoyed in the United States as one of its greatest assets. Associates of Mr. Netanyahu’s say that he understands that as much as anyone.

“Netanyahu is smart enough to know that Obama may well be the president after the elections as well,” said Moshe Arens, a former Israeli ambassador to Washington and a onetime mentor to Mr. Netanyahu. “He’s no dumbo.”