The cords that connect Israel to the United States were under unprecedented strain last night after Barack Obama publicly chided Prime Minister Benjamin Netanyahu as part of his long-awaited address to the Muslim world at Cairo University in Egypt.
While the 55-minute speech was billed as an effort by the President to soothe grievances of Muslims in the Middle East and beyond towards America, particular attention was always going to be paid to his remarks on the Israeli-Palestinian conflict.
Full though it was with rhetorical embellishments, the speech was blunt and plain-spoken. And Mr Obama showed he is willing to get firm with Israel.
Thus he made public a festering and personal argument with Mr Netanyahu, who is refusing to heed his demands for a halt to all new settlements in the occupied West Bank.
Mr Obama said the US-Israeli bonds were “well known” and “unbreakable”. Then he said Washington “doesn’t accept the legitimacy of continued Israeli settlements”.
Mr Obama executed a familiar oratorical trick, admitting the US may in the past have succumbed too easily to stereotypes about Islam, while telling his audience Islam needed to stop making the same mistake with America.
“That same principle must apply to Muslim perceptions of America. Just as Muslims do not fit a crude stereotype, America is not the crude stereotype of a self-interested empire,” he said.
He was forthright in saying that nothing he was saying detracted from the real horror perpetrated by the 9/11 terrorists. “America can never tolerate violence by extremists,” he added.
As with many in his target audience, there will be sceptics in the US who doubt Mr Obama's words, however finely spoken, will change very much on the ground.
From the outset the risk was that the delicate alchemy of America's relationship with Israel would be upset by this address. Some would argue that only by showing a new willingness to take Israel to task, can Mr Obama hope to heal rifts with Muslims.
But there was balance built into the Cairo speech. He deplored Holocaust deniers and said that threatening Israel with destruction was “deeply wrong”.
Today he visits the former Nazi concentration camp in Buchenwald, Germany.