Israeli Defense Minister Ehud Barak said Monday, April 30 he had little confidence that key talks between Iran and world powers would succeed in resolving the standoff over Tehran's disputed nuclear programme, AFP reported.

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.

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.

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.