JERUSALEM -- Israel's prime minister, Benjamin Netanyahu, moved quickly to block even tentative steps by Iran and the United States to ease tensions and move toward negotiations to end the nuclear crisis, signaling what is likely to be a sustained campaign by Israel to head off any deal.
Mr. Netanyahu's office dismissed as "media spin" a flurry of statements by Iran's new president, Hassan Rouhani, about the goals of his nation's nuclear program and his willingness to engage in diplomacy regarding it. His remarks were made amid news that Mr. Obama had reached out to Mr. Rouhani with a private letter, and renewed discussion in Washington of negotiations that could lift sanctions against Iran.
"There is no need to be fooled by the words," said a lengthy statement issued late Thursday in response to Mr. Rouhani's interview this week with NBC News. "The test is not in what Rouhani says, but in the deeds of the Iranian regime, which continues to advance its nuclear program with vigor while Rouhani is being interviewed."
Mr. Netanyahu, who has described Mr. Rouhani as a "wolf in sheep's clothing," has stepped up his longstanding campaign against Iranian nuclear development in recent days, and plans to make it the focus of his Sept. 30 meeting with President Obama in Washington and his upcoming speech to the United Nations General Assembly.
Washington and Jerusalem share the goal of preventing Iran from obtaining a nuclear weapon, but have often disagreed on the timetable and strategy for doing so. Israel, which sees an Iranian bomb as a threat to its existence, has pressed for a more forceful and immediate military threat. The United States, while stressing that all options are on the table, has urged Israel to hold its fire and give diplomacy and sanctions more time. Tehran maintains that its nuclear development is for civilian purposes.
"It's certainly different perspectives looking at the same picture," said Dore Gold, president of the Jerusalem Center for Public Affairs and a former Netanyahu aide. "Israel is clearly focused on Iranian action, and the messages in Washington seem more hopeful about Iranian intentions."
Since Mr. Netanyahu's United Nations speech last year laying out his red lines on Iran, and especially since Mr. Obama's visit to Israel in March, the two countries have seemed more in sync. But many Israeli leaders and analysts saw Mr. t Obama's handling of the Syrian chemical weapons situation over the last month as a bad omen for his resolve in stopping Iran.
"Netanyahu's words were most likely meant for the ears of the members of Congress, so they will not let Obama get carried away by Rouhani's overtures," Ron Ben-Yishai, a respected journalist, wrote in an analysis published on Ynet, an Israeli news site. "The Israelis are also telling their American counterparts that just like in the case of the Syrian crisis, a credible military threat is needed in order to get results on the diplomatic track."
Mr. Netanyahu himself said last week, "The message in Syria will also be heard very well in Iran," and, "The world needs to make sure that anyone who uses weapons of mass destruction will pay a heavy price for it." On Thursday, he reiterated a four-step formula he laid out two days before, saying, "The international community must increase the pressure on Iran" until it halts uranium enrichment, removes enriched uranium from the country, dismantles the Fordo nuclear plant and stops the plutonium track.
"Rouhani has boasted in the past about how he deceived the international community in nuclear talks, while Iran continued with its nuclear program," the statement from Mr. Netanyahu's office said. "The goal of the regime in Iran," it added, is a deal to "give up a secondary part of its nuclear program" but "preserve and fortify the principal element of its capabilities, which will allow it to race to obtain a nuclear weapon within a short time, the moment it chooses to do so."
Yuval Steinitz, Israel's minister for strategic affairs, said in an interview published Friday that the Iranians were six months away from developing a bomb, and that "there is no more time to hold negotiations." He told the right-leaning newspaper Israel Today that Washington's "all options on the table" catchphrase had not been enough.
"Today the Iranians take into account that they have room to maneuver, and that is the most dangerous thing," Mr. Steinitz said. "It must be understood that no one will come to help us if, heaven forfend, we lose the ability to defend ourselves."
In a separate development, the International Atomic Energy Agency on Friday rejected a bid put forward by Arab countries to criticize Israel for the nuclear arsenal it is believed to possess.
At an agency meeting in Vienna, the Arab states had proposed a nonbinding resolution expressing concern about "Israeli nuclear capabilities," calling on Israel to join a global antinuclear weapons treaty and to place its nuclear facilities under monitoring by the I.A.E.A., the United Nations nuclear agency.
An identical motion was passed by a slim majority four years ago, but defeated the following year under pressure from Western countries. In the past two years, Arab countries have refrained from introducing a similar motion so as not to undermine efforts to convene an international conference to free the Middle East of weapons of mass destruction, Israel Radio reported.
The United States had opposed this year's resolution, saying it would harm the broader diplomatic effort to eliminate such weapons.
Israel has long maintained a policy of nuclear ambiguity, neither confirming nor denying that it possesses nuclear weapons.
The I.A.E.A. vote "demonstrates that there is significant international understanding for Israel's vital national security interests given the threats and challenges it faces in the region," said Jeremy Issacharoff, deputy director general for strategic affairs at Israel's Ministry of Foreign Affairs.
As for Mr. Rouhani's recent statements and actions in advance of his visit to the United States next week, Israeli experts on Iran differed on what to make of them. Emily Landau of the Institute for National Strategic Studies at Tel Aviv University said she saw "no indication of any willingness to reverse course on the nuclear front," citing 1,000 recently installed centrifuges and Mr. Rouhani's insistence that he will not consider suspending uranium enrichment.
"Rouhani is no moderate as far as Israel is concerned," Ms. Landau said in an e-mail Friday afternoon. "One of his first foreign policy statements accused Israel of being behind the crisis in Syria, and now he adds that Israel, the 'warmonger,' is responsible for all instability in the region."
But Meir Javedanfar, an Iranian-Israeli lecturer at the Interdisciplinary Center in Herzliya who wrote a book on Iran's nuclear program, said Friday that Mr. Rouhani could be promising real change and that a meeting between him and Mr. Obama would be positive for Israel.
"As a result of the sanctions, the regime in Iran is under real pressure, and Rouhani comes to save the regime" Mr. Javedanfar told Israel Radio. "If Rouhani does the work, this is good for Israel. If the Iranians do the job, our pilots and soldiers don't have to."
Mr. Netanyahu, for his part, did not limit his criticism of Mr. Rouhani to the nuclear question. His statement also addressed the Iranian president's ducking of a question in his NBC interview about whether he, like his predecessor, believed that the Holocaust was a myth.
Mr. Rouhani answered, "I'm not a historian, I'm a politician." Mr. Netanyahu's statement declared, "It does not take a historian to recognize the existence of the Holocaust -- it just requires being a human being."
Isabel Kershner contributed reporting.
This article originally appeared in The New York Times.