Israeli Defence Minister Ehud Barak said Monday he had little confidence that key talks between Iran and world powers would succeed in resolving the standoff over Tehran's disputed nuclear programme.

While Barak said the barrage of international sanctions imposed on Iran has clearly worked and forced the Islamic Republic to sit down and talk, he was not hopeful that the talks would lead anywhere.

"Today sanctions are stronger than ever. They've forced the Iranians to take note, to sit down and to talk," he told journalists at a meeting of the Foreign Press Association in Jerusalem.

"The P5+1 engagement with Iran, however, does not fill me with confidence. I may sound pessimistic but the state of Israel cannot afford to be duped."

Six world powers, known as the P5+1 grouping of diplomats from the United States, Russia, China, Britain, France and Germany, held a first round of talks with Iran in Istanbul on April 14, with a second, more in-depth round due to take place in Baghdad on May 23.

"They say a pessimist is merely an optimist with experience," he quipped.

"In this case, you don't have to look back too far to understand the tactics of Iran. And while I hope to be proven wrong, as Israel's minister of defence I have responsibility to the people of Israel not to ignore the risks."

The UN Security Council has slapped four rounds of sanctions on Tehran over suspicions harboured by Israel and much of the West that Iran is seeking a militarised nuclear capability -- a charge which Tehran denies.

Rather than taking the necessary steps to scale back its nuclear programme, Iran was getting closer to the "zone of immunity" when their facilities would be protected from any external strike, Barak said.

"Actions speak louder than words. On the ground, the Iranians keep moving and are determined to obtain nuclear weapons," he said.

"And they are getting closer. We are approaching what I've termed the immunity zone -- the moment when Iran's nuclear programme will be sufficiently developed and secretly concealed, that it will be immune to any surgical attacks."

Of special concern is Iran's formerly secret Fordo site which is located deep inside a mountain bunker near the holy city of Qom, where its centrifuges are enriching uranium to 20 percent purity.

Israel has not ruled out a preemptive strike on Iranian nuclear facilities, and Barak said that as long as Iran posed a future existential threat to the Israeli people, all options remained open.

"It is well understood in Washington DC as well as in Jerusalem, that as long as a there is a future existential threat to our people, all options to prevent Iran from getting nuclear weapons should remain on the table -- and they will," he said.

"I have enough experience to know by now that the military option will be complicated with certain associated risks. But a nuclear Islamic Republic of Iran would be far more dangerous, both for the region and to the whole world.

"Our number one consideration is to ensure that our fate will remain firmly in our hands."