A change in the Iranian leadership could open the way for renewed peace between the Islamic republic and Israel, Binyamin Netanyahu, the Israeli Prime Minister, said at the start of a brief European visit that will focus on the threat posed by Iran’s nuclear ambitions.

But one of his aides said that even if pro-reform protests succeed in forcing a change in Iran’s president, it was unlikely greatly to diminish the danger from a potentially nuclear-armed Iran, which Mr Netanyahu deems an existential threat to the Jewish state.

“As long as there’ll be an Islamic regime in place, I don’t think there’ll be a change in Iran’s nuclear policy,” said Avi Pazner, an advisor to the Prime Minister, who has made the Iranian threat the centrepiece of his foreign policy. He said that even if reformist Mir Hossein Mousavi should emerge triumphant from the standoff — which is deemed unlikely at this stage by Israel — Tehran was unlikely to relinquish its nuclear ambitions.

In earlier comments published in Bild, the German newspaper, Mr Netanyahu said that free and fair elections that led to a new leadership could end decades of hostility between the two countries.

“Under a different regime, the friendly relations that prevailed in the past could be restored,” Mr Netanyahu said. “If they had a free choice, I have no doubt they would have a different government . . this is a theocratic, totalitarian and brutal state that doesn't really give a free choice to the Iranian people.”

Mr Netanyahu has refused to rule out the possibility of an Israeli military strike to destroy Iran’s nuclear capabilities, although international analysts predict that such a raid would be extremely risky for Israel and the entire region.

When he met President Obama this year in Washington, Mr Netanyahu urged him not to spend too long trying to engage Iran in a meaningful dialogue to resolve the tensions surrounding its nuclear reactors, which Tehran claims are designed purely to produce power, not bombs.

Before he departed for America, it emerged that Leon Panetta, the CIA head, had visited Israel secretly to obtain assurances that the new right-wing leadership was not planning any surprise attacks on Iran, whose hardline President, Mahmoud Ahmedinejad, has in the past threatened to “wipe Israel off the map”.

With Mr Ahmedinejad facing increasing international criticism for his brutal crackdown on protesters claiming fraud in last week’s elections, Mr Pazner said that there was a question hanging over “American willingness or ability to engage in a meaningful dialogue with the current regime”.

To that end, Mr Netanyahu will be calling for tougher sanction against Iran’s nuclear programme during his visit to Paris and Rome, hoping to use the rising antipathy to the regime’s crackdown to bolster support for Israel’s tough approach toward the Islamic republic.

Many Israeli commentators have noted that a victory for Mr Ahmedinejad in the elections would favour Israel’s uncompromising stance towards a nuclear Iran. However, an assessment this week by the head of Mossad, Meir Dagan, that Iran was still five years away from acquiring nuclear capacity took some of the sting out of Israel’s dire warnings, much to the ire of right-wing hawks.

“If the project has no technical glitches, and if Iran’s programme does not malfunction in any way, they will have a bomb to launch by 2014," the spy chief told the parliamentary Foreign Affairs Committee. “This is a significant existential threat for the State of Israel. We must distance this threat.”

Other military and intelligence officials have predicted in the past that Iran could have a nuclear bomb much sooner than that.

Israeli officials have so far declined to comment on whether a harsh crackdown on Iran’s opposition protests could accelerate an Israeli strike. Ephraim Halevy, a former Mossad chief, said that no one was sure what would be the outcome of the Iranian unrest, which other security chiefs have predicted will fizzle out or be put down by the authorities.

“If you wanted someone to tell you what will happen, you would be better served by seeing a science-fiction movie,” he said at a public meeting on Sunday.

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