Israel's military chief toned down the rhetoric over Iran's nuclear programme on Wednesday, describing the Iranian leadership as "very rational" and unlikely to take the decision to build a bomb.

Speaking to Haaretz newspaper, Lieutenant General Benny Gantz said Iran was approaching the point at which it would be able to decide on whether to build a bomb, but that Supreme leader Ayatollah Ali Khamenei had not yet decided "whether to go the extra mile."

So far, Israel and Washington do not believe that Tehran has actually taken the decision to develop a nuclear bomb, a decision which would require the ability to quickly produce weapons-grade uranium.

"In my opinion, he would be making a huge mistake if he does so, and I don't think he will want to go the extra mile," he said of Khamenei.

"I think the Iranian leadership is composed of very rational people," he said, indicating that the international regime of hard-hitting sanctions was "starting to bear fruit."

Defence Minister Ehud Barak also took a somewhat softer line on Iran, saying it had "not yet decided to manufacture atomic weapons" and suggesting the sanctions could work.

"If the Americans, and the Europeans and we ourselves are determined, there is a change of stopping the Iranians before they acquire the atomic bomb," he told Israeli public radio.

Israel and much of the West suspect Iran is using its civilian nuclear programme as a cover for a weapons drive -- a charge which Tehran vehemently denies, and Israeli officials have refused to rule out a pre-emptive strike to prevent it from happening.

But there was no sign of any change in the hardline approach of Prime Minister Benjamin Netanyahu, who said Tehran should remain under biting sanctions until it halts all uranium enrichment.

"They have to stop all enrichment," he told CNN, saying he would not accept Iran enriching uranium to even three percent, which is near the level required for peaceful atomic energy.

Iran has already developed the capacity to enrich uranium to 3.5 percent, and to 20 percent, which is used to create medical isotopes, but it would have to enrich to 90 percent in order to make nuclear weapons.

The language used by Gantz in Wednesday's interview was far from the fiery rhetoric of Netanyahu, who last week said anyone who refused to acknowledge the Iranian threat had learned nothing from the Nazi Holocaust during World War II.

"They are afraid to speak the truth, which is today, as it was then, that there are people who want to annihilate millions of Jews," he said.

The attempt by both Gantz and Barak to tone down the rhetoric on Iran comes after a spate of media reports suggesting a division within the Israeli leadership over how to handle the Iranian issue.

Two months ago, Netanyahu and Barak appeared to agree that the sanctions imposed on Iran would not work, Haaretz reported, describing the political leadership as "divided" between the premier and the defence minister, and other top ministers who wanted to give the sanctions time to work.

But last week, the paper said there was a growing rift between the two after Netanyahu criticised the nuclear talks between world powers and Iran.

"Netanyahu's tough statement also appears to underline the growing rift between him and Defence Minister Ehud Barak on the Iran issue," the paper said, indicating that Barak "has said he believes the negotiations should be given a chance to succeed."

Barak, it said, does not categorically oppose 20 percent enrichment under complete supervision and is willing to accept 3.5 percent enrichment, while Netanyahu "opposes any enrichment of uranium by Iran."

Reports of an apparent rift were confirmed by a senior Israeli official, who spoke to AFP on condition of anonymity.

"Gantz is only repeating publicly what military leaders, including his predecessor General Gabi Ashkenazi, have continuously told the politicians in the last few years," he said.

"Ehud Barak has evolved and seems more moderate. And (Foreign Minister) Avigdor Lieberman recently told Israeli reporters it was necessary to give a chance to the economic sanctions and diplomatic pressure, that we must give it time and not hurry," he said.

"In fact, the prime minister is somewhat isolated on Iran," he said.

Analysts believe that a decision to attack Iran could not be taken without the full support of the defence minister and most of the security cabinet, as well as the backing of the Israeli military and the Mossad spy service.