WASHINGTON - The gap between Israel and the United States on Iran widened Sunday as Benjamin Netanyahu insisted on a "red line" from Washington as Tehran was "90 per cent" towards having a nuclear weapon.

The Israeli leader, speaking on two US political talk shows, pressed the need for a categorical bar on Iran, saying such a safeguard had averted nuclear calamity with Russia during the Cold War and could do so again.

The United States says all options against Iran, including military action, remain on the table, but top officials reject so-called "red lines" as political grandstanding that might leave them at a strategic disadvantage.

To CNN and in a second interview with NBC - both aired Sunday - Netanyahu maintained that telling Iran there is a definite line it must step back from would serve as a pre-emptive and effective deterrent.

"If they know there's a point, a stage in their enrichment or other nuclear activities that they cannot cross because they'll face consequences, I think they will actually not cross it," he told CNN. "It's important to put a red line before them and that's something we should discuss with the United States."

The Israeli prime minister said Iran was moving rapidly to complete enrichment of the uranium needed to produce a nuclear bomb. "In six months or so they'll be 90 per cent of the way there," he said.

But his call for a change of tack and stiffer warnings from Washington was rejected by Susan Rice, the US ambassador to the United Nations.

Rice maintained there was "no daylight" between US and Israel on preventing Iran from acquiring a nuclear weapon, but her comments on the timescale of Tehran's ambitions jarred with Netanyahu's judgment.

"We think that there's still considerable time for this pressure to work," Rice said, refusing to acknowledge the red lines argument and insisting that US sanctions were working.

"Their economy is beginning to buckle. Their oil production is down 40 per cent. Their currency has plummeted 40 per cent in the last year."

But she added: "This is not an infinite window, and we've made very clear that the president's bottom line is Iran will not have a nuclear weapon."

Israel has consistently said a nuclear-armed Iran would pose an existential threat to the Jewish state and has wielded the threat of military action, but the United States favors sanctions and diplomatic arm twisting.

Major Western powers agree with Israel that Tehran is using its civilian nuclear program as a cover for building atomic weapons capability, a charge the Iranians have repeatedly denied.

But with relations between Netanyahu and President Barack Obama viewed as frosty, US Defence Secretary Leon Panetta on Friday further highlighted the policy split.

"The fact is, look, presidents of the United States, prime ministers of Israel or any other country - leaders of these countries don't have, you know, a bunch of little red lines that determine their decisions," Panetta said.

"What they have are facts that are presented to them about what a country is up to, and then they weigh what kind of action is needed to be taken in order to deal with that situation," he told Foreign Policy magazine.

"I mean, that's the real world. Red lines are kind of political arguments that are used to try to put people in a corner."

The White House was last week forced to deny a report that Obama had refused to meet Netanyahu in New York later this month, and said the two spoke by telephone on Tuesday and were united in their stance toward Tehran.

And with Republican presidential nominee Mitt Romney accusing Obama of being a poor friend to Israel, Netanyahu has denied that he is guilty of meddling in US politics ahead of elections on November 6.

Rice said in a separate interview with "Fox News Sunday" that US-Israeli relations were "stronger than ever," and insisted the only reason Netanyahu and Obama would not meet at the upcoming UN General Assembly in New York was because their schedules did not match.

But Senator John McCain, the Republican candidate who lost to Obama in 2008, said there was a clear gap between Israel and the White House on where the red line lies.

"In the administration's view, it's when (Iran) has a nuclear weapon," and in Israel's view its when Tehran has "reached the level where they can quickly assemble a nuclear weapon," McCain told CBS's "Face the Nation" talk show.

"That's a big difference," he said.