The Israeli prime minister hit out at Iranian President Hassan Rouhani in his speech to the United Nations yesterday, calling him a “a wolf in sheep’s clothing.”

Mr Netanyahu warned the General Assembly that Mr Rouhani’s sweet-talking visit to the USA last week was a “ruse”, designed to buy time while his country builds its nuclear weapons.

He 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.”

Likening a nuclear Iran to “another 50 North Koreas”, Mr Netanyahu added: “It would make the spectre of nuclear terrorism a clear and present danger.”

The Israeli prime minister made it clear that Israel was prepared to face Iran alone if necessary.

He said: “I want there to be no confusion on this point. Israel will not allow Iran to get nuclear weapons. If Israel is forced to stand alone, Israel will stand alone. Yet in standing alone, Israel will know that we will be defending many, many others.”

His UN speech followed meetings with President Barack Obama and Secretary of State John Kerry in Washington on Monday, where he stressed the need to maintain strong economic sanctions against Iran.

Following their meeting, Mr Obama assured Mr Netanyahu that Iran’s conciliatory words to the US would not be enough for the sanctions to be lifted.

He said: “We have to see if in fact they are serious about their willingness to abide by international norms and international law and international requirements and resolutions.”