Israeli Prime Minister Benjamin Netanyahu said Sunday the world should keep up pressure on Iran to rein in its nuclear programme and avoid thinking the election of a moderate president will bring change.

"The international community should not fall into wishful thinking and be tempted to ease pressure on Iran to stop its nuclear programme," Netanyahu said at the start a meeting of his cabinet.

"Iran will be judged on its actions," he said a day after Hassan Rowhani, a moderate cleric and former top nuclear negotiator, was declared the winner of Iran's presidential election.

"If it insists on continuing to develop its nuclear programme the answer needs to be clear -- stopping its nuclear programme by any means," Netanyahu said.

"In the past 20 years the only thing that brought about a temporary freeze in Iran's nuclear programme was the fear of aggressive action against it."

Intelligence Minister Yuval Steinitz said although Rowhani won the support of reformists, it was still supreme leader Ayatollah Ali Khamenei who called the shots.

"The working assumption should be that Khamenei, who has been heading this (programme) for 24 years, will continue to head it and therefore without continued pressure on Iran there is no chance of seeing significant change in nuclear policy," said Steinitz.

"Rowhani doesn't consider himself a reformer, he defines himself as a conservative. He was... Khamenei's representative to the National Security Council," he told army radio.

Israel, the region's sole if undeclared nuclear power, along with the West accuses Iran of using its atomic energy programme as a cover for developing an atomic bomb. Tehran vehemently denies those claims.

It also charges Tehran with aiding Lebanon's Shiite Hezbollah movement and the Palestinian militant group Hamas, both bitter enemies of the Jewish state.

Justice Minister Tzipi Livni preferred to reserve judgement on Rowhani.

"The test will be in his actions," she said on army radio. "It is impossible to know today."

"The Iranians now have a moderate face but if it emerges that in substance he is also a more moderate man, and if what truly happened is that the Iranian people want more moderation and if there is also pressure to have better relations with the West, then the test will move to the West."

Suzanne Maloney, senior fellow at The Saban Center for Middle East Policy at the Brookings Institution, was upbeat.

"Rowhani is an ideal candidate to spearhead a new initiative to wrest Iran from its debilitating battle with the international community over the nuclear issue," she said in a blog ahead of the Iranian poll.

The mass-circulation Israel Hayom daily, considered close to Netanyahu, showed a smiling Rowhani and his dancing supporters on its front page, with the headline "'Moderate', but what about the bomb?"

Writing in the top-selling Yediot Aharonot daily, veteran Middle East affairs correspondent Smadar Perry, argued Rowahani's background and connections could actually help bring about change, if he seeks it.

"It is part of the Iranian president's job definition to sell Iran to the outside world," she wrote.

"Rowhani has promised to improve the image of the Islamic republic and use his connections to reduce its international isolation.

"By virtue of his proximity to authority, his long career and his religious background he will not be restrained -- at least not during his first 100 days of grace," she added.

In the same paper, Yigal Sarna said Netanyahu would miss outgoing president Mahmoud Ahmadinejad, whose strident anti-Israel rhetoric played to Israel's attempts to enlist worldwide diplomatic opposition.

"What will we do without the scarecrow, the fanatic Ahmadinejad?" he asked. "What will we do without the Persian Hitler... We are either going to have return to reality or quickly find ourselves a new Satan."