Defense Minister Ehud Barak said on Thursday an Israeli attack on Iran is not imminent but all options remain open to stop what Israel sees as an Iranian bid to develop nuclear weapons.
"We have no intention, at the moment, of taking action, but the State of Israel is far from being paralyzed by fear," Barak told Israel Radio. "It must act calmly and quietly -- we don't need big wars."
Iran says its nuclear energy program is wholly peaceful.
The UN nuclear watchdog, citing intelligence reports, said last month Iran appeared to have worked on designing an atom bomb and may still be pursuing secret research to that end.
Barak was interviewed a day after the top US military officer said he did not know whether Israel would alert the United States ahead of time if it decided to strike Iran, the Jewish state's arch-adversary in the Middle East.
General Martin Dempsey, the chairman of the Joint Chiefs of Staff, also acknowledged differences in perspective between the United States and Israel over the best way to handle Iran and its nuclear program.
Dempsey said the United States was convinced that sanctions and diplomatic pressure were the right ways to take on Iran, along with "the stated intent not to take any options off the table" -- diplomatic language that leaves open the possibility of future military action.
"I'm not sure the Israelis share our assessment of that. And because they don't and because to them this is an existential threat, I think probably that it's fair to say that our expectations are different right now," Dempsey told Reuters.
Iran is facing new sanctions following the UN report.
In the radio interview, Barak said "Israel would be very glad if sanctions and diplomacy could bring the Iranian leadership to a clear decision to abandon its nuclear military program."
But, "unfortunately, I think that is not going to happen."
Asked about Dempsey's remarks, Barak said Israel "greatly respects the United States" and maintained a continuous dialogue with its main ally on security issues.
"But one must remember that ultimately, Israel is a sovereign nation and the Israeli government, defense forces and security services -- not others -- are responsible for Israel's security, future and existence," Barak said.
"Certainly, a non-diplomatic option is the last option, and I think everyone agrees with the fact that all options are on the table," the Israeli defence chief said.
Dempsey, asked directly whether Israel would alert the United States ahead of time if it chose to go forward with military action against Iran, replied flatly: "I don't know."
Last week, US Defense Secretary Leon Panetta raised American concerns about the unintended consequences of any military action against Iran during talks with Barak at a security forum in Canada.
Those include US fears about fallout on the world economy and that a strike would only delay -- not derail -- an Iranian nuclear program whose known sites are widely dispersed and fortified against attack.
The Islamic Republic has warned that it will respond to any attacks by hitting Israel, widely believed to be the Middle East's only nuclear power, and US interests in the Gulf.