Israel’s prime minister Benjamin Netanyahu declared on Tuesday that his country will never allow Iran to get nuclear weapons, even if it has to act alone, and dismissed Iranian President Hassan Rouhani’s “charm offensive” as a ruse to get relief from sanctions.

Mr. Netanyahu, speaking to world leaders at the U.N. General Assembly, played the spoiler to Iran’s overtures to warm ties with the U.S. after decades of estrangement. Last week, the U.S. and Iranian presidents spoke on the phone, the highest level contacts between their countries in 34 years.

Mr. Netanyahu said Israel’s future is threatened by a “nuclear-armed” Iran seeking its destruction and urged the international community to keep up pressure through sanctions.

“Israel will not allow Iran to get nuclear weapons,” he said. “If Israel is forced to stand alone, Israel will stand alone, but in standing alone Israel will know that we will be defending many, many others,” Mr. Netanyahu added.

Iran’s U.N. Ambassador Mohammad Khazaee shot back, “Unlike Israel, Iran would not and did not attack any country.”

Exercising Iran’s right of reply in the assembly, he added- “It is not due to its inability, but due to its principled policy in rejecting any use of force. ... Therefore the Israeli prime minister had better not even think about attacking Iran let alone planning for that.”

At the White House, press secretary Jay Carney said Mr. Netanyahu’s scepticism about Iran and its intentions is “entirely justifiable” because until recently Iran’s leadership “was pledging to annihilate Israel.” He said the U.S. share’s Israel’s goal of keeping Iran from obtaining a nuclear.

Mr. Carney stressed that Mr. Obama will be “very firm” on demanding verifiable, transparent action to ensure that Iran has given up its nuclear weapons ambitions.

Mr. Netanyahu said a nuclear-armed Iran would have a choke-hold on the world’s main energy supplies.

“It would trigger nuclear proliferation throughout the Middle East, turning the most unstable part of the planet into a nuclear tinderbox. And for the first time in history, it would make the spectre of nuclear terrorism a clear and present danger,” the Israeli leader said.

Mr. Netanyahu said the greater the pressure, the greater the chance for diplomacy to succeed. He said the only diplomatic solution that would work is one that requires Iran to completely dismantle its nuclear weapons programme and prevents it from starting one in the future.

This would require a halt to all uranium enrichment, removing uranium stockpiles from Iran, dismantling the infrastructure for “nuclear breakout capability” reaching the point where the country can make a quick dash to a nuclear weapon.

Mr. Netanyahu called Mr. Rouhani “a loyal servant of the regime” and stressed that he has done nothing to stop Iran’s nuclear program since his election in June.

Mr. Rouhani was at the U.N. last week and presented a more moderate face of the hard-line clerical regime in Tehran.

The parties agreed to meet again in Geneva on Oct. 15-16 for more substantive negotiations.

Iran insists its nuclear activities are for peaceful purposes only and that it does not seek a weapon.

Mr. Netanyahu asserted that Mr. Rouhani must have known about the murder of 85 people in a terror attack on the Jewish Community Centre in Buenos Aires and the killing of 19 American soldiers in Saudi Arabia in 1996 because he was head of Iran’s Supreme National Security Council from 1989-2003.

The U.S. has also accused Iran of sponsoring acts of terrorism around the world throughout the 1990s. Iran and its proxy Hezbollah were blamed for a 1992 attack on the Israeli Embassy in Buenos Aires, Argentina, that killed 29 people, and the attack on a Jewish community centre there two years later.

Some analysts linked Iran’s Quds Force to helping direct the 1996 bombings of the Khobar Towers in Saudi Arabia that killed 19 American military personnel.

Mr. Netanyahu said Mr. Rouhani condemned the “violent scourge” of terrorism.

“Yet in the last three years alone, Iran has ordered, planned or perpetrated terrorist attacks in 25 countries on five continents,” he charged, without providing any evidence to back up the accusation.

Mr. Netanyahu said Mr. Rouhani launched his “charm offensive” because tough sanctions from the U.N., the U.S. and many others “have taken a big bite off the Iranian economy” and the regime is under intense pressure from the Iranian people to get the sanctions lifted.

“Ahmadinejad was a wolf in wolf’s clothing. Mr. Rouhani is a wolf in sheep’s clothing, a wolf who thinks he can pull the wool over the eyes of the international community,” Mr. Netanyahu said.

Mr. Netanyahu also accused Iran of lamenting the human tragedy in Syria, but at the same time directly participating in President Bashar Assad’s murder and massacre of tens of thousands of innocent men, women and children. He said Iran’s regime is propping up the Syrian regime that just used chemical weapons against its own people.

Mr. Netanyahu took apart Mr. Rouhani’s speech to the General Assembly last week, saying he wished he could believe the Iranian president’s words “but we must focus on Iran’s actions and it’s the brazen contrast, this extraordinary contradiction between Mr. Rouhani’s words and Iran’s actions that is so startling.”

Mr. Netanyahu said Iran has not crossed the “red line” that he set at last year’s General Assembly but claimed Mr. Rouhani has done nothing to stop the country’s uranium enrichment program or its development of intercontinental ballistic missiles (ICBMs) “whose sole purpose is to deliver nuclear warheads.”

“And Iran is building now ICBMs that the United States says could reach this city (New York) in three or four years,” Netanyahu said.

“Yet Iran is actively destabilizing Lebanon, Yemen, Bahrain and many other Middle Eastern countries,” Mr. Netanyahu said.

Israel’s Shin Bet security agency says Iran recruited the Belgian-Iranian national Ali Mansouri last year and sent him to Israel to spy. He was arrested on Sept. 11 at Israel’s international airport.

A lawyer for Mansouri said the allegations are baseless.

Israel announced the arrest on Sunday as Netanyahu left to the U.S. for talks on Iran. Israeli media have speculated that the timing of the announcement was politically motivated.

“I wish I could believe Rouhani but I don’t because facts are stubborn things,” Mr. Netanyahu said, “and the facts are that Iran’s savage record flatly contradicts Rouhani’s soothing rhetoric.”

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