US Defence Secretary Leon Panetta has warned that Iran must either negotiate acceptable limits on its nuclear programme or face the possibility of US military action to stop it from getting the bomb.
Panetta made his remarks Wednesday outside a city in southern Israel, with an "Iron Dome" anti-rocket defence system as a backdrop.
Panetta said repeatedly that "all options", including military force, are on the table to stop Iran, should sanctions and diplomacy, the preferred means of persuasion, ultimately fail.
Israeli Defence Minister Ehud Barak, standing beside Panetta, said he sees an "extremely low" probability that sanctions will ever compel Iran to give up its nuclear activities.
Panetta arrived in Israel on Tuesday after meeting in Cairo with Egypt's new president and its military chief.
Speaking before the talks, Panetta said Wednesday's discussion with Prime Minister Binyamin Netanyahu and Defence Minister Ehud Barak will be "more about what is the threat we are confronting" in Iran's nuclear programme and about sharing intelligence information.
In Cairo, Panetta denied Israeli press reports that he planned to share with the Israelis any US plans for military action against Iran.
Iran says its nuclear work is for civilian energy uses, but suspicions that the Islamic republic will use enriched uranium for nuclear weapons has resulted in international sanctions and sabre-rattling from Israel, which perceives a nuclear Iran as an existential threat.
The United States has discouraged Israel from a unilateral, pre-emptive military strike on Iran, but has said it would keep all options available.
"What we are discussing are various contingencies and how we would respond," Panetta said. Asked whether any such contingencies include plans for potential military action against Iran, he said, "We obviously continue to work on a number of options in that area."
Al Jazeera's Cal Perry, reporting from Jerusalem, said Panetta was reluctant to discuss military options.
"Normally, what he would do is walk that fine line, saying Israel had the right to defend itself without talking about military options, but Israel officials are trying to push that line of discussion."
Stronger than ever
The Panetta visit comes just days after US Republican presidential hopeful Mitt Romney met with top Israeli officials about Iran and other issues. Romney has accused the Obama administration of being too soft on Iran and not providing sufficient support to Israel.
Greeting Panetta on Wednesday at Israeli defence headquarters, Barak said, "The defence ties between Israel and the United States are stronger and tighter than they have ever been and the credit now has to go, most of it, to you, Leon."
Panetta responded: "We are a friend, we are a partner, we have, as the defence minister has pointed out, probably the strongest US-Israel defence relationship that we have had in history. What we are doing, working together, is an indication not only of our friendship but of our alliance to work together to try to preserve peace in the future."
Netanyahu told Israeli Channel 2 TV on Tuesday that despite reservations about an Iranian attack among former Israeli security officials and Israel's current army chief, the country's political leadership would make the final decision on any attack.
"I see an ayatollah regime that declares what it has championed: to destroy us," Netanyahu said. "It's working to destroy us, it's preparing nuclear weapons to destroy us. ... If it is up to me, I won't let that happen."
With "matters that have to do with our destiny, with our very existence, we do not put our faith in the hands of others, even our best of friends," Netanyahu said, hinting that Israel might act alone despite American misgivings.
Netanyahu said both Romney and Obama have said "Israel has the right to defend itself".