The White House has turned down an offer by Israeli Prime Minister Benjamin Netanyahu to meet with President Obama later this month, U.S. and Israeli officials confirmed to Fox News.

Though the White House is citing scheduling conflicts, the chilly reception is sure to be seen as a snub among Israel’s biggest defenders – and it comes amid a state of heightened alert over Iran’s nuclear program and the possibility of Israeli action.

Sources said Netanyahu, though he plans to be in New York City during his brief stay, was offering to travel to D.C. to make the meeting happen. However, the White House apparently said Obama’s tight schedule – the president is in the middle of a feverish campaign run -- would make a meeting difficult.

White House spokesman Tommy Vietor later confirmed to Fox News that Obama is not expected to meet with Netanyahu, though insisted it was just a scheduling problem. He said Obama will be at the United Nations on Sept. 24 and leave the following day, while Netanyahu won’t be in the city until later in the week.

“They're simply not in the city at the same time,” Vietor said.

He also said Netanyahu and Obama are in “frequent contact,” and that Netanyahu has instead been offered meetings with Secretary of State Hillary Clinton and other top officials.

But the turn-down comes amid increasing international anxiety about Iran’s nuclear program. The U.N. reportedly has found new intelligence showing Iran is moving toward nuclear weapon capability. And the exchange between the White House and the prime minister’s office is the most recent in what is seen as a cool, if not strained, relationship between Obama and Netanyahu, despite Israel being considered one of the United State’s closest allies.

“I’m astounded that (Obama) cannot find the time,” former U.S. Ambassador to the United Nations John Bolton said. “I don’t see it so much as a snub as a horrible, substantive mistake in American foreign policy.”

One well-placed Jewish-American leader told Fox News that the White House has not yet fully ruled out moving things around on the schedule to accommodate Netanyahu. But as of now, Obama is scheduled to be on the campaign trail during the window of time when Netanyahu can make it to Washington.

“Discussions are ongoing,” the source emphasized.

Asked about relations between the two men, the source acknowledged they “are not warm and fuzzy” and that there is “a lot of tension” between the two governments, given the gravity of the issues under consideration. But overall, the source said the alliance remains strong, particularly in terms of military-to-military cooperation, and even in day-to-day interactions “up to and including the prime minister.”

Republicans were quick, though, to pounce on the news. Rep. Ted Poe, R-Texas, tweeted: “How ironic that the #POTUS has time for high dollar $40K-a-head fundraiser with @JayZ and @Beyonce but not for the PM of Israel.”

The prime minister’s office told the White House that Netanyahu’s official visit will be short, starting on a Thursday and ending at sundown Friday because of the Sabbath. He is staying in the U.S. through Sunday. One Israeli source said he “wouldn’t be surprised if things changed” regarding a meeting by the time Netanyahu arrives.

Netanyahu will still travel to speak at the United Nations headquarters.

Earlier on Tuesday, Netanyahu launched an unprecedented critique of the U.S. government and others over their stance on the Iranian nuclear program, according to the English-language news site Haaretz.

"The world tells Israel 'wait, there's still time,’” the site quotes Netanyahu as saying. “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."

Obama has increased economic sanctions on Iran but has yet to define the so-called “red line” -- which, should Iran cross it, would theoretically result in military action.

"Now if Iran knows that there is no red line … what will it do?” Netanyahu asked Tuesday. “Exactly what it's doing. It's continuing, without any interference, towards obtaining nuclear weapons capability and from there, nuclear bombs."

Democrats upset Israel supporters last week when they removed language in the party platform that acknowledged Jerusalem as the capital of Israel.

The president, though, had the words re-inserted and said in his acceptance speech that the country’s commitment to Israel's security “must not waver.”

“And neither must our pursuit of peace,” he continued.