The Jewish state at this point did not intend to launch a strike against Iranian nuclear facilities, but retained the option as a "last resort," Defense Minister Ehud Barak told Israel Radio.
"We don't need unnecessary wars. But we definitely might be put to the test," he said.
Barak said he hoped that sanctions and diplomacy would pressure the Iranian leadership to abandon its suspected nuclear weapons program, but did not expect that to happen.
Israel, like the West, is convinced Iran is developing a nuclear bomb, despite Tehran's insistence that its nuclear program is designed to produce energy.
Israel says a nuclear-armed Iran would threaten the Jewish state's survival, citing Iranian President Mahmoud Ahmadinejad's repeated references to Israel's destruction, Iran's arsenal of ballistic missiles and its support for militant groups that fight Israel.
The U.S. -- as well as some security experts in Israel -- have loudly opposed the prospect of an Israeli military strike against Iranian nuclear facilities, because of its potential for touching off retaliation against Israel and a broader, regional conflagration.
But Barak suggested that Israel might not alert world powers before embarking on a strike.
"Israel is a sovereign state and it is the government of Israel, the Israeli army and security forces who are responsible for Israel's security, future and survival," he said.
Mysterious blasts, computer viruses and assassinations have disrupted Iran's nuclear program, and there has been speculation of Israeli involvement.
Barak would not comment on that possibility, but said, "We are not happy to see the Iranians move ahead on this (program), so any delay, be it divine intervention or otherwise, is welcome."
In a reflection of Israeli concerns over Iran, the Israeli army said Thursday that it has launched a project to teach Farsi, the dominant language in Iran, to Israeli high school students in hopes of preparing them for careers in military intelligence.
An army intelligence official said a select group of 23 honors students had been carefully chosen to participate in the three-year course. An intelligence commander in uniform comes to their school to teach the course, and soldiers from the intelligence unit help them with homework.
"The need for Persian instruction is obvious," the official said, speaking on condition of anonymity in line with army protocol.
A few dozen high-school students graduated this year from a similar pilot course in high-level Arabic. Most of them subsequently enlisted into Israel's army intelligence, the official said.