US-Israeli relations faced crisis Tuesday after Prime Minister Benjamin Netanyahu said Washington had no moral right to stop Israel striking Iran, in an election-year rebuke to President Barack Obama.

Deepening tensions between the Obama administration and the Israeli government were also revealed in news that Obama had declined to rearrange his busy campaign schedule to meet Netanyahu in New York later this month.

The Israeli leader angered Obama aides, who have seen Republicans accuse the president of throwing Israel "under the bus," when he publicly criticized Washington's refusal to set "red lines" for action on Iran's nuclear program.

"The world tells Israel: Wait, there's still time. And I say: wait for what? Wait until when?" Netanyahu said in English on Tuesday, in comments clearly aimed directly at the White House.

"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," he said.

Later, as Obama honored victims of the September 11 attacks, the Haaretz newspaper quoted an Israeli official as saying Obama had declined Netanyahu's request for talks during the UN General Assembly in New York this month.

An Israeli official also told AFP: "So far the response has been that Obama's very tight schedule does not allow such a meeting."

Publicly, the White House said the lack of expected talks was purely a matter of scheduling. Privately, officials were angered at the latest Israeli outburst on Iran, a key issue in Obama's tough re-election fight.

"They're simply not in the city at the same time," National Security Council spokesman Tommy Vietor said.

Obama is due to arrive on Monday, September 24 and to leave the next day while Netanyahu is not due in New York until later in the week, Vietor said.

"But the president and prime minister are in frequent contact and the prime minister will meet with other senior officials, including Secretary (of State Hillary) Clinton, during his visit."

Haaretz said Netanyahu was even ready to travel to Washington to meet Obama but the White House rejected his request.

However, a senior US official told AFP that there had never been a request by the Israelis for such talks.

The dispute came amid fervent speculation that Netanyahu could order a unilateral strike on the Islamic Republic's nuclear program.

The White House says there is still time for diplomacy and sanctions to change Iranian behavior, though warns Obama is ultimately prepared to use force to stop the Islamic Republic getting a nuclear weapon.

Washington has been unwilling to publicly state "red lines" for action, fearing that Iran will trigger an immediate crisis by going right up to them in a game of nuclear brinkmanship.

On Monday, Clinton said the United States was "not setting deadlines" on Iran, and State Department spokeswoman Victoria Nuland said Tuesday that Washington would prefer to keep talk about Iran with Israel private.

Netanyahu's latest maneuvering comes less than two months before the US presidential election, and as Republican Mitt Romney accuses Obama of deserting Israel in its hour of need and appeasing Iran.

With an eye on the votes of American Jews, Romney even traveled to Israel in July, and an aide suggested that if Romney were president, the US definition of the immediacy of the Iranian threat would be closer to Netanyahu's definition than Obama's.

The White House argues that no president has done more than Obama to protect Israel, militarily and diplomatically -- for instance blocking a Palestinian drive for statehood at the United Nations.

Israel views Iran's nuclear program as an existential threat and portrays Tehran as approaching a critical point in its capacity and knowledge of the process of enriching uranium for nuclear weapons.

Obama has repeatedly stressed that he will not allow Iran to get to the point of actually manufacturing a weapon, a semantic difference which portrays the threat as less immediate.

Furthermore, Washington believes it has sufficient intelligence capability to determine if Iran decides to cross that threshold and has enough time between following any such decision to act.

Defense Secretary Leon Panetta told CBS News Tuesday that "it's roughly about a year right now. A little more than a year."

Iran denies it is seeking nuclear weapons.

Obama and Netanyahu have had a history of tense public meetings. When they last met in March, Netanyahu warned that Israel must remain the "master of its fate" in a firm defense of his right to mount a unilateral strike on Iran.

The year before, Netanyahu sparked fury among White House officials when he delivered a stinging public lecture to Obama on the history of the Jewish people in the Oval Office.

Last year at the UN, however, Netanyahu seemed keen to mend the relationship, saying Obama deserved "a badge of honor" for protecting the Jewish people.