"I believe it is well understood in Washington, as well as in Jerusalem, that as long as there is an existential threat to our people, all options to prevent Iran from getting nuclear weapons should remain on the table," Ehud Barak told a meeting of journalists covering Israel and the Palestinian territories.
"Parts of the world, including some politically motivated Israeli figures, prefer to bury their heads in the sand," Barak told the Foreign Press Association journalists Monday.
A growing number of current and former Israeli security officials have spoken out against an Israeli strike on Iran.
Israeli military Chief of Staff Lt. Gen. Benny Gantz said in remarks published Wednesday he did not believe Iran would build a nuclear bomb.
Two days later, Yuval Diskin, former director of the Israeli internal security agency Shabak, or Shin Bet, said Israel's "messianic" political leaders were misleading the public on the level of effectiveness of a military strike and he had no faith in them, citing "experts" who predicted a military strike would actually speed up Iran's nuclear program, with Tehran using an attack to legitimize its efforts.
Barak conceded Monday a military strike "would be complicated with certain associated risks."
"But a radical Islamic Republic of Iran with nuclear weapons would be far more dangerous both for the region and, indeed, the world," he said.
Economic sanctions against Iran were "stronger than ever," forcing Tehran "to take note, to sit down and to talk," Barak told the journalists.
Despite that progress -- and a threat of tighter U.S. economic sanctions to take effect July 1 -- Barak said he was not filled "with confidence."
"I may sound pessimistic, but the state of Israel cannot afford to be duped," he said.
"They say a pessimist is merely an optimist with experience," he later said.
Iran is in the midst of negotiations with six world powers, known as the P5 plus 1, or the five permanent members of the U.N. Security Council -- the United States, Russia, China, France and Britain -- plus Germany.
The first round of talks was in Istanbul, Turkey, April 14, with Iranian negotiators appearing more flexible and open to resolving the crisis than the West expected, The New York Times reported.
A second round of talks is set for Baghdad May 23.
U.S., Israeli and European officials, supported by U.N. weapons inspectors, maintain Iran plans to build nuclear weapons. Tehran insists its nuclear program is for peaceful civilian uses only.
Israel has repeatedly said it would not let Iran reach nuclear-weapons capacity and has declared it has an option to launch a military strike against Iran's nuclear facilities as a last resort.