During an aggressive speech at the United Nations this week, Prime Minister Benjamin Netanyahu of Israel used sarcasm and combative words to portray Iran’s new president, Hassan Rouhani, as a smooth-talking charlatan, one who is determined to continue building a nuclear weapons arsenal.
Mr. Netanyahu called Mahmoud Ahmadinejad, the previous Iranian president, “a wolf in wolf’s clothing” and Mr. Rouhani “a wolf in sheep’s clothing.”
Mr. Netanyahu has legitimate reasons to be wary of any Iranian overtures. So do the United States and the four other major powers who are involved in negotiations over Iran’s nuclear program.
But it could be disastrous if Mr. Netanyahu and his supporters in Congress were so blinded by distrust of Iran that they exaggerate the threat, block President Obama from taking advantage of new diplomatic openings, and sabotage the best chance to establish a new relationship since the 1979 Iranian revolution sent American-Iranian relations into the deep freeze.
Mr. Rouhani and the Iranian foreign minister, Mohammad Javad Zarif, have insisted repeatedly that Iran wants only to develop nuclear energy. Obtaining a nuclear weapon, they say, would harm the country’s security.
Even so, Iran hid its nuclear program from United Nations inspectors for nearly 20 years. The country is enriching uranium to a level that would make it possible to produce bomb-grade nuclear material more quickly.
Iran has also pursued other activities, such as developing high-voltage detonators and building missiles that experts believe could only have nuclear weapons-related uses. These facts make it hard not to view the upcoming American-brokered negotiations skeptically.
But Mr. Netanyahu has hinted so often of taking military action to keep Iran from acquiring a nuclear weapon that he seems eager for a fight. He did it again at the United Nations this week, warning that Israel reserved the right to strike Iran’s nuclear facilities if it deemed that Iran was close to producing nuclear weapons. “Against such a threat, Israel will have no choice but to defend itself,” he said.
The Iranians were so angered by what they called Mr. Netanyahu’s “inflammatory” speech that they issued a rebuttal. They spoke of the need to “sustain the current positive atmosphere” so that diplomacy could be successful.
Similarly, they were not happy that President Obama, meeting Mr. Netanyahu at the White House this week, took a harsher tone toward Iran than he did when he spoke by phone with Mr. Rouhani last week.
Both Mr. Obama and Mr. Rouhani have hard-line domestic audiences and allies they will need to consider and cajole as they undertake this effort to resolve the nuclear dispute and develop a new relationship. For Mr. Obama, that means working closely with Israel.
That includes helping Mr. Netanyahu see that sabotaging diplomacy, especially before Iran is tested, only makes having to use force more likely. That would be the worst result of all.