Israel's Benjamin Netanyahu on Tuesday winds up a high-profile US visit focused on Iran's perceived nuclear threat after warning that his country would not live in the "shadow of annihilation."

Netanyahu was to meet with US Secretary of State Hillary Clinton and visit the US Congress a day after keenly-watched talks withPresident Barack Obama against the backdrop of speculation over a possible Israeli strike on Iran.

"Unfortunately, Iran's nuclear program has continued to march forward. Israel has waited ... for diplomacy to work, we've waited for sanctions to work. None of us can afford to wait much longer,"Netanyahu told some 13,000 attendees late Monday in a speech before the AIPAC pro-Israel lobbying group.

"As prime minister of Israel I will never let my people live in the shadow of annihilation."

While Clinton has voiced exasperation in the past over settlement building in the occupied West Bank and east Jerusalem under Netanyahu, he enjoys strong bipartisan backing on Capitol Hill.

Netanyahu saluted Congress during his speech before the American Israel Public Affairs Committee, saying that more than half the legislature's members were guests in the audience and leading the crowd in a standing ovation.

"Democrats and Republicans alike, I salute your unwavering support for the Jewish people," he said.

Netanyahu will meet Congressional leaders on Tuesday, winding up the two-day visit in which he held crucial talks with Obama earlier on Monday over how best to thwart Iran's nuclear ambitions.

The Obama administration has signaled that it does not yet believe Iran has taken a decision to develop a nuclear weapon, or that the time is right for military action, preferring to give biting new sanctions time to work.

However Israel, which sees a possible Iranian nuclear weapon as a threat to its existence, believes that Iran may be on the cusp of "break out" capacity -- the moment when it could quickly produce weapons-grade uranium.

In his speech before the American Israel Public Affairs Committee, Netanyahu said Israel has "exactly the same policy" as the Obama administration.

"We're determined to prevent Iran from developing nuclear weapons, we leave all options on the table and containment is definitely not an option."

Netanyahu said that for the world to allow Iran -- which he said was dedicated to the destruction of the Jewish state -- to attain a nuclear arsenal evoked memories of US refusal in World War II to bomb the Auschwitz Nazi death camp to prevent the mass extermination of Jews there.

"My friends, 2012 is not 1944," he said.

Netanyahu told Obama on Monday that Israel must remain the "master of its fate" in a firm defense of his right to mount a unilateral strike on Iran.

Obama assured Netanyahu he had Israel's "back" but also stressed that he saw a "window" for diplomacy, despite rampant speculation Israel could soon mount a high risk go-it-alone military operation.

The leaders, who have had a famously testy relationship, met for two hours of talks amid clear signs of differences on the imminence of the perceived Iranian nuclear threat, if not its ultimate danger to both nations.

In an impassioned on-camera statement, Netanyahu told Obama: "Israel must have the ability always to defend itself, by itself, against any threat."

A senior US official said Washington now believed after the meeting that Netanyahu understood that Obama was deeply serious about preventing Iran acquiring nuclear weapons.

The US official said the administration believed it would have up to a year to decide on how to respond should Iran decide to begin enriching uranium to weapons-grade quality.

Israel does not share that timetable, but an Israeli official said his country's concerns were now also widely understood, without elaborating.

Obama meanwhile faces a rising chorus of election-year criticism from Republicans, who say he has failed to halt Iran's nuclear drive and vow tougher action should they retake the White House in November's election.

Senate Republican leader Mitch McConnell told AIPAC that if Iran enriches uranium to weapons-grade level or decides to develop atomic weapons, the United States should use "overwhelming force" to end its nuclear program.

"In the weeks and months ahead, Israel and the United States face a day of reckoning," he said.

"We either do what it takes to preserve the balance of power within the broader Middle East, or risk a nuclear arms race across the region that's almost certain to upend it."