Moshe Yaalon, a former military chief of staff whose portfolio includes monitoring Iran, said he believes Iran is at least three years away from developing a nuclear bomb. Iran denies such intentions.
Israeli military officials have said Iran has the expertise to build a bomb, but still needs time to gather the necessary materials. Yaalon's assessment matches the outer range of past Israeli estimates that Iran is anywhere from one to three years away from developing a weapon.
"These difficulties postpone the timetable, so we can't talk about a point of no return. Iran does not currently have the ability to produce a nuclear weapons by itself," he told Israel Radio. "It could happen in the next three years if the process succeeds. I hope it won't succeed at all and that the Western world's effort will ultimately bring about Iran not having a nuclear capability."
Israel considers Iran a strategic threat because of its nuclear program, missile capability and frequent references by Iranian President Mahmoud Ahmadinejad to the destruction of Israel.
Israel has repeatedly warned in recent years that Iran was close to developing a nuclear weapons, only to revise its assessments. Yaalon acknowledged that evaluating Iran's secretive nuclear program is an imprecise science, noting that under past assessments he delivered while in the military, Iran should already have achieved weapons capability.
Yaalon did not say how he reached his latest assessment. In recent months Iranian nuclear scientists have been abducted and killed, and a destructive computer worm has struck Iran's uranium enrichment activity.
Iran insists its nuclear program is peaceful and has accused Israel of trying to sabotage it.
Israel officially supports the diplomatic efforts in place to curb Iran's nuclear ambitions, but has not ruled out the possibility of a military strike.
The U.N. Security Council has imposed four rounds of sanctions on Iran in June after Tehran refused to halt its disputed nuclear program. The council's five permanent members, along with Germany, are set to hold a new round of talks with Iran in late January.
Israel considers Iran its most dangerous enemy because of its nuclear program, missiles and calls for Israel's destruction. Iran also supports the anti-Israel Hamas and Hezbollah militant groups.