JERUSALEM — Prime Minister Benjamin Netanyahu on Monday reiterated his willingness to attack the Iranian nuclear program without support from Washington or the world, returning to an aggressive posture that he had largely abandoned since his United Nations speech in September.

“When David Ben-Gurion declared the foundation of the state of Israel, was it done with American approval?” Mr. Netanyahu asked in an interview broadcast on Israel’s Channel 2 on Monday night. “When Levi Eshkol was forced to act in order to loosen the siege before 1967, was it done with the Americans’ support?

“If someone sits here as the prime minister of Israel and he can’t take action on matters that are cardinal to the existence of this country, its future and its security, and he is totally dependent on receiving approval from others, then he is not worthy of leading,” Mr. Netanyahu added. “I can make these decisions.”

Though American officials, including President Obama, have always acknowledged that Israel ultimately has the right to decide how to defend itself, Mr. Netanyahu’s tough tone and timing — on the eve of the American presidential election — are sure to reignite rifts with Washington over how best to prevent Tehran from developing a nuclear bomb.

As has been the case over the past two years, however, it is impossible to know whether his hawkish words are harbingers of deeds or part of a strategic campaign to scare nations into increasing economic and diplomatic pressure on Iran.

“I am not eager to go to war,” Mr. Netanyahu said in the seven-minute interview. “I have been creating very heavy pressure, and part of this pressure comes from the knowledge some of the most powerful nations in the world have that we are serious. This isn’t a show, this is not false.”

Besides the creation of diplomatic tensions if Israel were to act alone against Washington’s wishes, there is a more practical concern: the Israeli military lacks the capacity to penetrate all of Iran’s underground nuclear facilities, and thus could most likely only delay the potential development of a nuclear weapon by a few years. The United States has bunker-busting bombs that could do far more damage.

The interview was broadcast on “Fact,” a program often compared to “60 Minutes,” at the end of an hourlong documentary on Israeli decision making regarding Iran over the past decade. The program highlighted the opposition of Israel’s own security establishment to a unilateral strike, saying that Mr. Netanyahu and his defense minister, Ehud Barak, ordered the Israel Defense Forces to prepare for an imminent operation in 2010 but were rebuffed by the chiefs of their military and international intelligence service.

Among those interviewed was Ehud Olmert, the former prime minister currently contemplating a political comeback. He accused Mr. Netanyahu of “spitting in the face” of Mr. Obama and “doing anything possible to stop him from being elected president of the United States,” a harsh critique in a country that regards safeguarding its special relationship with Washington as a sacred priority.

“What’s all this talk, that we will decide alone on our fate and that we won’t take anybody else into consideration?” said Mr. Olmert, who is expected to make Mr. Netanyahu’s relationship with Mr. Obama a mainstay of his campaign if he runs. “Can someone please explain to me with which airplanes we will attack if we decide to attack alone, against the opinion of others — airplanes that we built here in Israel? With which bombs will we bomb, bombs that we made by ourselves? With which special technologies will we do it, those that we made by ourselves or those that we received from other sources?”

But when shown a video of Mr. Olmert’s retort, Mr. Netanyahu was not cowed. “If what I just heard is that on this matter which threatens our very existence, we should just say, we should just hand the keys over to the Americans and tell them, ‘You decide whether or not to destroy this project, which threatens our very existence,’ well, that’s one possible approach, but it’s not my approach,” he said. “My approach is that if we can have others take care of it, or if we can get to a point where no one has to, that’s fine; but if we have no choice and we find ourselves with our backs against the wall, then we will do what we have to do in order to defend ourselves.”

After years in which Mr. Netanyahu and Mr. Barak pursued the Iranian threat in close partnership, the prime minister now seems virtually alone in his defiant stance, as other leaders attempt to distinguish their positions ahead of Israeli elections on Jan. 22. While Mr. Netanyahu said in his Sept. 27 speech at the United Nations that the critical moment for preventing Iran from developing a weapon would most likely come next spring, Mr. Barak last week pushed the timetable back further, and offered a new explanation of Israel’s reduced sense of urgency.

The crux of Mr. Barak’s argument, made in an interview with Britain’s Daily Telegraph, was based on reports by the International Atomic Energy Agency, the most recent in August, showing that Iran had 189 kilograms, about 416 pounds, of uranium enriched to the 20 percent level — from which it could relatively easily be further enriched to weapons grade. Roughly half of that was diverted to civilian use in a form that could not be easily turned into bomb fuel. But Iran has continued production and by most estimates, at current rates, would have roughly a bomb’s worth by next summer.

That “allows contemplating delaying the moment of truth by 8 to 10 months,” Mr. Barak said.

But several high-ranking Israeli officials and analysts said that Mr. Barak’s explanation was overly simplistic. While the diversion was clearly a factor, they said, it was not a new development: the nuclear agency had reported a similar transfer of enriched uranium in May, and that had hardly cooled the rhetoric of either Mr. Barak or Mr. Netanyahu through the summer. And both men have long warned of secret centrifuges that could be spinning without outside knowledge, enabling rapid replenishment of the enriched stockpile.

“Netanyahu backed away because he was getting the message that he was going too far and this could do damage, this was not helpful either to Israel or to stopping Iran,” said Emily Landau, an Iran expert at the Institute for National Security Studies at Tel Aviv University. “It might be easier for Barak to now say that it’s because of the technical issue, but it’s not a real issue. Relations with the United States is a much more substantial, real issue, but it’s more difficult to give that as your explanation.”

Graham Allison, a Harvard professor of government who specializes in international security, called Mr. Barak’s statement “kind of a convenient excuse,” adding that “the reason they really blinked” was that the prime minister was unable to convince a majority of his cabinet of the wisdom of acting alone.

“The big phenomenon here is what I’ve called the revolt of the Israeli security barons,” Mr. Allison said. “I can’t think of a prior Israeli government or an analogous case anywhere where there’s such a clear gap between a prime minister on one hand and his security establishment on the other.”