Washington's unprecedented backing for a UN resolution for a nuclear-free Middle East that singles out Israel has both angered and deeply worried the Jewish state although officials are cagey about openly criticising their biggest ally.
The resolution adopted by the United Nations on Friday calls on Israel to join the Non-Proliferation Treaty (NPT) and urges it to open its facilities to inspection.
It also calls for a regional conference in 2012 to advance the goal of a nuclear-free Middle East.
Israel is widely believed to be the only nuclear power in the Middle East, with around 200 warheads, but has maintained a policy of deliberate ambiguity about its capabilities since the mid-1960s.
The document, which singles out Israel but makes no mention of Iran's controversial nuclear programme, drew a furious reaction from the Jewish state who decried it as "deeply flawed and hypocritical."
But it was US backing for the resolution which has caused the most consternation among Israeli officials and commentators, who interpreted the move as "a resounding slap around the face" which has dealt a very public blow to Israel's long-accepted policy of nuclear ambiguity.
Publicly, the Israel government has not criticised the US position but privately, officials expressed deep disappointment over the resolution, which Washington backed despite intensive Israeli efforts to block it.
According to the top-selling Yediot Aharonot daily, the government of Prime Minister Benjamin Netanyahu was "furious with the Obama administration for having failed to prevent the resolution from passing... and for choosing to support it."
"The American support for the resolution, after decades in which it supported Israel on this issue, came as a complete surprise," the paper said.
"In the secret talks that Netanyahu held with Obama's men... Israel was promised that the resolution would not focus on Israel and that if it did, the Americans would vote against."
The left-leaning Haaretz daily said Israel had been "sacrificed by the US on the altar of a successful conference" in what constituted "a diplomatic victory for Egypt" which has campaigned against Israel's nuclear arsenal.
Five years ago, the paper recalled, Obama's predecessor George W. Bush, refused to accept parts of a draft document calling on Israel to join the NPT and dismissed the idea of holding talks to create a nuclear-free Middle East -- even at the cost of the conference's failure.
The controversial resolution was passed just days ahead of a key meeting between Obama and Netanyahu aimed at restoring friendly ties between the two allies which had been soured over a dispute about Jewish settlements.
But the Maariv daily said that Obama's 'last minute' invitation for Netanyahu to visit the White House had clearly been planned with the NPT review conference in mind.
"It is reasonable to assume that the Americans knew they were going to deliver a blow to Israel's policy of nuclear ambiguity and that Obama wanted to try to minimize the damage," the paper said.
The move draws a line under a long-held "agreement" between Israel and Washington dating back to 1969 under which the Jewish state was permitted to keep silent on its country's nuclear potential while holding back from any nuclear test.
In return, Washington agreed not to exert or allow any pressure on Israel over its nuclear capabilities.
"It is an undeniably negative change to US policy" with regards to Israel's nuclear programme, said Eitan Gilboa, an analyst from Bar Ilan University near Tel Aviv.
Pointing to contradiction between Obama both applauding the resolution and criticising it for singling out Israel, Gilboa said Washington was "losing its leadership role because of the naive and unrealistic" outlook of its president