The White House declined Israeli Prime Minister Benjamin Netanyahu's request on Tuesday to meet U.S. President Barack Obama during a UN conference in New York at the end of the month.

The White House National Security Council Spokesman Tommy Vietor told Haaretz the two would not meet due to a scheduling conflict. "The President arrives in New York for the UN on Monday, September 24th and departs on Tuesday, September 25th. The Prime Minister doesn’t arrive in New York until later in the week. They're simply not in the city at the same time."

Vietor did, however, say that Netanyahu and Obama are "in frequent contact" and that the PM would meet with other senior officials, including U.S. Secretary of State Hillary Clinton.

An official in Jerusalem said that the Prime Minister's Office sent the White House a message stating that although Netanyahu will spend only two and a half days on U.S. soil, he is interested in meeting Obama and is willing to travel to the U.S. capital specifically for that purpose. The official added that the White House rejected the request and said that at this time Obama's schedule does not allow for a meeting.

Asked whether the president is ready to meet Netanyahu in Washington, Vietor said: "I don’t have a final schedule for the president for that whole week."

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The White House's response marks a new low in relations between Netanyahu and Obama, underscored by the fact that this is the first time Netanyahu will visit the U.S. as prime minister without meeting the president.

Defense Minister Ehud Barak tried to ease the tension on Tuesday, saying that the differences between the U.S. and Israel should be ironed out "but behind closed doors."

"We must not forget that the U.S. is Israel's most important source of support in terms of security," he said in a statement.

Earlier on Tuesday, Netanyahu launched an unprecedented verbal attack on the U.S. government over its stance on the Iranian nuclear program.

"The world tells Israel 'wait, there's still time'. And I say, 'Wait for what? Wait until when?' 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 told reporters on Tuesday.

"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," he said.

U.S. Department of State spokeswoman Victoria Nuland stressed again on Tuesday that the U.S. administration doesn't see public discussion of Iranian nuclear program and red lines as useful. "We don't think it's particularly useful to have those conversations in public. It doesn't help the process and it doesn't help the integrity of the diplomacy. To be standing here at the podium parsing the details of the Iranian nuclear program is not helpful to getting where we want to go," she said, briefing the media.

White House spokesman Jay Carney reasserted the strong cooperative relationship between Israel and the U.S. on security. "We have extensive and ongoing conversations and contact with our close ally, Israel, on this issue as well as a wide variety of other security-related issues. We have the most comprehensive security and intelligence relationship with Israel in history, as attested to by not just leaders from this administration but from the Israeli government."

Also on Tuesday, U.S. Defense Secretary Leon Panetta said that if Iran decides to make a nuclear weapon, the United States would have a little more than a year to act to stop it.

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