Defying US President Barack Obama, Israeli Prime Minister Benjamin Netanyahu flew to Washington late yesterday to warn Congress about the risks of a possible nuclear deal with Iran in a speech that has imperilled ties between the two allies.

Israel fears that Obama’s Iran diplomacy, with an end-of-March deadline for a framework accord, will allow its arch foe to develop atomic weapons – something Tehran denies seeking.

But by accepting an invitation from the Republican party to address Congress tomorrow, the Israeli leader infuriated the Obama administration, which said it was not told of the speech before plans were made public in an apparent breach of protocol.

Earlier this week, Obama’s national security adviser, Susan Rice, said the partisanship caused by Netanyahu’s looming address was “destructive to the fabric of US-Israeli ties”. But Netanyahu, who is running for re-election in a March 17 ballot, has framed his visit as being above politics and he portrayed himself yesterday as being a guardian for all Jews.

“I’m going to Washington on a fateful, even historic, mission,” he said as he boarded his plane in Tel Aviv.

I’m going to Washington on a fateful, even historic, mission

“I feel that I am an emissary of all Israel’s citizens, even those who do not agree with me, and of the entire Jewish people,” he told reporters.

US officials fear he is seeking to sabotage the Iran diplomacy. While White House and Israeli officials insist that key areas of cooperation from counter-terrorism to intelligence to cyber security will remain unaffected, the deepening divide over the Iran talks is shaping up as the worst in decades.

Previously Israel has always been careful to navigate between the Republican and Democrat camps. The planned address, however, has driven a rare wedge between Netanyahu’s government and some congressional Democrats. Some two dozen or more of them plan to boycott the speech, according to unofficial estimates.

US Secretary of State John Kerry said yesterday the US deserves “the benefit of the doubt” to see if a nuclear deal can be reached. Speaking on the ABC programme This Week, Kerry also said he hoped Netanyahu’s speech to Congress did not turn into “some great political football”.

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