In an interview conducted at the World Economic Forum in Davos, Switzerland, and published by The Daily Beast on Friday, Mr. Barak was asked if there was any way Israel could go to war with Iran over what many in the West believe is a nuclear weapons program without dragging in the United States.

Mr. Barak replied that there were more than just the two options — of full-scale war or allowing Iran to obtain nuclear weapons capability — in the event that sanctions and diplomacy failed.

"What we basically say is that if worse comes to worst, there should be a readiness and an ability to launch a surgical operation that will delay them by a significant time frame and probably convince them that it won't work because the world is determined to block them," he said.

Under orders from the White House, "the Pentagon prepared quite sophisticated, fine, extremely fine, scalpels," Mr. Barak added, referring to the ability to carry out pinpoint strikes.

Herbert Krosney, an American-Israeli analyst and the author of a book about the arming of Iran and Iraq, said Mr. Barak's statement now "indicates that there is close cooperation" between Israel and the United States following months of tension between the country's leaders (though military and intelligence services continued to work together closely).

"I think there is a realization in Israel that it would be extremely difficult for Israel to operate alone," he said.

Last year, Prime Minister Benjamin Netanyahu of Israel was pushing hard for the Obama administration to set clear "red lines" on Iran's nuclear progress that would prompt the United States to undertake a military strike, infuriating the administration. And Mr. Barak repeatedly warned that because of Israel's more limited military capabilities, its own window of opportunity to carry out an effective strike was closing.

It has appeared that Mr. Barak has drifted away from Mr. Netanyahu in recent months, sounding more conciliatory toward the Obama administration, but even the prime minister has become less antagonistic.

The Pentagon declined to comment on The Daily Beast report, but a senior defense official said, "The U.S. military constantly plans for a range of contingencies we might face around the world, and our planning is often quite detailed." The official added, "That shouldn't come as a surprise to anyone."

In recent years, Mr. Barak and Mr. Netanyahu had become increasingly alarmed as Iran moved forward with a nuclear program that it says is solely for peaceful purposes, but that Israel, the United States and others believe is geared toward producing a bomb. The two men consistently emphasized Israel's doctrine of self-reliance for such existential issues.

But faced with tough opposition from Washington and public criticism from a string of former Israeli security chiefs, the prospect of an imminent unilateral Israeli strike receded in recent months.

In the past few weeks Mr. Netanyahu campaigned for re-election in Israel as a strong leader who, among other things, had managed to persuade the world to deal with the Iranian threat.

Mr. Netanyahu and his conservative Likud Party emerged weakened from the elections, with much of the Israeli electorate more focused on domestic issues. In a speech after the voting, he said, "The first challenge was and still is to prevent Iran from acquiring nuclear weapons." But he did not again threaten to go it alone.

In the interview last week, Mr. Barak did not specify what the Pentagon's "scalpels" were. But there has been a broad effort at the White House, the Pentagon and the intelligence agencies to develop a series of options that could set back, though probably not halt, Iran's nuclear progress.

The first was a covert plan called Olympic Games to undermine Iran's nuclear enrichment plans with cyberattacks, according to participants in that program. The second layer of plans, American and other officials have said, involves covert means of interrupting the supply of uranium to Iran's enrichment plants, or crippling the plants themselves. The biggest target is a deep underground plant called Fordo, near Qum. There, under a mountain, Iran is producing most of its medium-enriched uranium, which could be converted to bomb grade in a matter of months.

The site is hardened, and probably beyond Israel's ability to destroy from the air. The United States recently added a weapon that officials believe could do significant damage: the "Massive Ordnance Penetrator," a bomb that is designed to attack deep, hardened sites.

But the existence of any plans, officials note, does not indicate an intent to them carry them out.

Elisabeth Bumiller and David E. Sanger contributed reporting from Washington.