The White House has reportedly rejected a request by Binyamin Netanyahu, the Israeli prime minister, to meet President Barack Obama when he travels to the US later this month for the UN General Assembly.
An Israeli official told the Reuters news agency, on condition of anonymity, that Netanyahu's aides had asked for a meeting in Washington, but "the White House has got back to us and said it appears a meeting is not possible ... that the president's schedule will not permit that."
The Obama administration had previously angered its Israeli counterparts by insisting that Israel hold off on a direct attack against Iranian targets, as Netanyahu issued strong remarks condemning opposition to a military strike.
White House officials have denied that any political differences were behind the apparent snub.
"They're simply not in the city at the same time," Tommy Vietor, White House spokesman, said, adding that Obama and Netanyahu were in "frequent contact" and that Israel's leader would see Secretary of State Hillary Clinton during his trip.
Netanyahu has met Obama on each of his previous US trips as Israeli leader since 2009.
The move is unusual, especially so close to an election, when the support of Jewish voters and donors is carefully courted.
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But most members of the Jewish-American community identify as Democrats, and will probably vote to re-elect President Obama anyway, Al Jazeera's Rosiland Jordan reported.
Earlier on Tuesday, Netanyahu had said that the international community could not ask Israel to keep waiting before "acting against Iran" if it has not laid down "red lines" over Tehran's suspected nuclear programme.
"The world tells Israel, 'Wait, there's still time.' And I say, 'Wait for what? Wait until when?'" he said.
"Those in the international community who refuse to put red lines before Iran don't have a moral right to place a red light before Israel."
Netanyahu, a former captain in Israel's special forces, reiterated his defence of Israel's "right" to attack Iran.
"So far we can say with certainty that diplomacy and sanctions haven't worked," he said.
"The sanctions have hurt the Iranian economy, but they haven't stopped the Iranian nuclear programme. That's a fact. And the fact is that every day that passes, Iran gets closer and closer to nuclear bombs.
"Now if Iran knows that there is no red line - if Iran knows that there is no deadline, what will it do? Exactly what it's doing. It's continuing, without any interference, towards obtaining nuclear weapons capability and from there, nuclear bombs."
|Al Jazeera's Rosiland Jordan
reports from the US State Department
The website of Israel's daily newspaper Haaretz called Netanyahu's words "an unprecedented verbal attack on the US government".
Relations between Obama and Israel's leadership have also been strained over Iran and other issues, such as Jewish settlement building in the occupied West Bank.
But Netanyahu had never framed in moral terms his differences with the current US president - who for his part has pledged he will "always have Israel's back" and is deep in a re-election campaign.
Meanwhile, Republican challenger Mitt Romney has accused Obama of throwing Israel "under the bus".
The position of Israeli leaders is not popular overseas, with Guido Westerwelle, Germany's foreign minister, stating his opposition to a unilateral Israeli strike against Iran during a meeting with Netanyahu on Sunday.
"Our goal remains a political and diplomatic solution," Westerwelle said.
In the US, a July poll carried out by the Council on Foreign Relations showed that US citizens favoured diplomacy over military action by almost four to one, with only 14 per cent of respondents believing the US government should encourage an Israeli attack on suspected Iranian nuclear sites.
At home in Israel, many public figures and former officials oppose Netanyahu's hawkish position, reportedly also now including Defence Minister Ehud Barak.
Meir Dagan, the former head of Israel's Mossad intelligence agency, recently told The New Yorker magazine that "an Israeli bombing would lead to a regional war and solve the internal problems of the Islamic Republic of Iran. It would galvanise Iranian society behind the leadership and nuclear issue."
He continued: "It would justify Iran in rebuilding its nuclear project and saying: 'Look, see, we were attacked by the Zionist enemy and we clearly need to have it'."
Iranian officials say the country, as a signatory to the nuclear Non-Proliferation Treaty, is entitled to develop nuclear energy infrastructure, and deny any attempts to build nuclear weapons.
Source: Al Jazeera and agencies