In an interview with the Maariv newspaper, Matan Vilnai said Israel was ready to face the consequences of a clash with Iran that could be sparked if the Jewish state decides to launch a strike against Tehran's nuclear programme.
But he warned that any military engagement should be weighed carefully, and cautioned that Israel should "always coordinate" with the United States.
"The assessments are for a war that will last 30 days on a number of fronts," he said, repeating the predictions of other senior Israeli officials that the Jewish state would suffer around 500 deaths in such a clash.
"It could be that there will be less fatalities, but it could be there will be more, that is the scenario that we are preparing for according to the best experts."
Speculation has risen in recent weeks about the possibility of an Israeli attack on Iran's nuclear programme, which the Jewish state and much of the international community believes masks a weapons drive.
Tehran vehemently denies those accusations, saying the programme is for peaceful energy and medical purposes.
As the speculation grows, observers in Israel have raised concern about the country's preparedness for war.
But Vilnai brushed aside such concerns, saying there was "no reason for hysteria."
"I can say in the most authoritative manner that the home front is ready as never before in the country's history," he said.
Vilnai declined to say whether he thought Israel should take military action against Iran, but warned any such decision required serious consideration.
"The only question is if a clash is necessary. War is something that is better to postpone and weigh carefully," he said, adding that he thought the Jewish state should coordinate its military activity with Washington.
"I don't want to be dragged into an argument, but I say that the United States is our greatest friend and we must always coordinate such things with it," he said.
Some Israeli officials have warned that the Jewish state could launch a unilateral attack on Iranian nuclear facilities if it believes Tehran is close to acquiring a nuclear weapon, even over objections from Washington.
Vilnai is set to be replaced by Avi Dichter, a former internal security minister and ex-head of the country's Shin Bet domestic intelligence agency.
The post, which Vilnai is leaving to become ambassador to China, was reportedly turned down by a slew of other top officials.
Israel is widely suspected to have the region's sole, if undeclared, nuclear arsenal.