Prime minister Benjamin Netanyahu and his government regard Iran as a more important defence issue than Syria.
Iran's nuclear programme remains priority for Israel
The Israeli prime minister, Benjamin Netanyahu, lost no time in warning the world about "wishful thinking" over Iran's suspected pursuit of a nuclear weapons capability following the election of Hassan Rowhani as Iranian president.
In Israel, where Iran's nuclear programme is considered as the weightiest foreign policy challenge - eclipsing even that of Syria - government officials and analysts point out that the Iranian supreme leader, Ali Khamenei, has the ultimate authority over the issue.
Although they were uniformly surprised by Mr Rowhani's election, they are sceptical about a nuclear policy shift under the new president even as Iran redoubles its attempts to have crippling sanctions against it lifted. Mr Rowhani's own comments at a news conference on Monday will have reinforced that scepticism.
The Israelis have been poring over the cleric's record as Iran's chief nuclear negotiator from 2003 to 2005. Mr Rowhani secured a deal in 2004 with the European Union, which subsequently collapsed amid acrimony, in which Iran agreed to freeze sensitive nuclear activities at its conversion plant in Isfahan.
But Israeli officials highlight comments he made in 2004 in which he boasted that his strategy had been to play for time with the Europeans. During the talks, he said: "We were installing equipment in parts of the facility in Isfahan. By creating a calm environment, we were able to complete the work there."
For the Israeli political establishment, such "game-playing" cannot continue. Iran now has an advanced and mature nuclear programme which is developing on a broad front - a far cry from 2004. And it has continued to make progress despite negotiations with the big powers. "The clock is ticking. A lot of time has been wasted," said a senior Israeli official.
For Emily Landau, a senior research associate with the Institute for National Security Studies, Mr Rowhani differs with the outgoing Iranian president, Mahmoud Ahmadinejad, in one major respect: the president-elect is interested in "maximum speed" for the nuclear programme at "minimum cost".
"That's why he's mad at Ahmadinejad," said Ms Landau, referring to the economic sanctions imposed under Mr Ahmadinejad's presidency, which have cost Iran billions of dollars in lost income. The two officials clashed during televised debates before the election.
She points out that Mr Rowhani, although identified as the sole reformist among the six candidates allowed to take part in the election, is "hard-wired into the regime".
"The regime ideology has targeted Israel from the beginning, including in things Rowhani said. It's not just Ahmadinejad," she said of the outoging president who has repeatedly questioned Israel's right to exist and denied the Holocaust.
Mr Netanyahu's comments were clearly aimed at warning the international community of the dangers of lifting the sanctions just because Mr Ahmadinejad is being replaced by a president who will symbolise reform.
"We've been there before. Remember Khatami?" said an Israeli official, referring to the failure of the former reformist president, Mohammad Khatami, who was outmanoeuvred by the supreme leader and the judiciary.
Israeli officials are clearly worried that in the light of Mr Rowhani's election, the P5+1 group - the US, UK, France, Russia, China and Germany - will agree to ease the sanctions without securing tough conditions in return, in particular a halt to Iran's uranium enrichment.
Although Iran continues to say that its nuclear programme is solely designed to produce electricity, it now has a stockpile of 182 kilograms of uranium enriched to 20 per cent - far higher than the 3.5 per cent grade required for reactor fuel.
Now that it has mastered the fuel cycle, and is continuing work on long-range missiles which could deliver a nuclear payload, analysts say that should Iran decide to break out of International Atomic Energy Agency supervision, it could quickly produce weapons-grade fuel.
Mr Netanyahu made it clear on Sunday that military action remains on the table, saying Israel would stop Iran building a bomb "by any means" - although officials say that there is room for a further round of sanctions targeting the oil industry.
Mr Netanyahu, in a speech to the United Nations last September, set a limit of 250kg on Iran's uranium enrichment at 20 per cent, a "red line" that could trigger military strikes if breached.
Yet Israeli officials and analysts concede that a credible military threat is lacking. The Iranian foreign minister, Ali Akbar Salehi, said in an interview with the French newspaper Le Figaro last week that Iran did not fear an Israeli military attack.
"It's clear we've all failed to convince them that we're serious," said an Israeli official.
Israel is the only nuclear weapons power in the Middle East, although its nuclear arsenal is not officially acknowledged, and the Israeli military has struck reactors in Iraq and Syria in the past in order to conserve its monopoly
One key question for the Israelis is President Barack Obama's resolve. One academic was critical of his hesitancy in responding to the Syrian regime's use of chemical weapons which he had established as a "red line".
"If he's afraid to stand up on that, can the Americans be trusted on Iran?" said Meir Litvak, director of the Alliance Centre for Iranian Studies at Tel Aviv University. "Obama has shown weakness. If I were Khamenei, I wouldn't be afraid of Obama."
Ms Landau, an advocate of limited military strikes targeting Iran's nuclear facilities as part of a broader strategy, also noted the issue of trust in Mr Obama. "Can he be trusted? Will he do what needs to be done?"
Anne Penketh is an international security analyst based in Paris
On Twitter: @annepenketh