WASHINGTON/JERUSALEM (Reuters) - Israeli Prime Minister Benjamin Netanyahu warned on Sunday that Iran would reach the brink of being able to build a nuclear bomb in just six or seven months, adding urgency to his demand that President Obama set a “red line” for Tehran amid the worst US-Israeli rift in decades.Taking to the airwaves to make his case directly to the American public, Netanyahu said that by mid-2013 Iran would have 90 percent of the material it needed for an atomic weapon. He again pressed the United States to spell out limits that Tehran must not cross if it is to avoid military action - something Obama has refused to do.“You have to place that red line before them now, before it’s too late,” Netanyahu told NBC’s “Meet the Press” program, saying that such a move could reduce the chances of having to attack Iran’s nuclear sites. The unusually public dispute between close allies - coupled with Obama’s decision not to meet with Netanyahu later this month - has exposed a gaping US-Israeli divide and stepped up pressure on the US leader in the final stretch of a tight presidential election campaign.It was Netanyahu’s most specific explanation yet on why he has become so strident in his push for Washington to confront Tehran with a more forceful ultimatum. At the same time, his approach could stoke further tensions with Obama, with whom he has had a notoriously testy relationship.US officials say Iran has yet to decide on a nuclear “breakout” - a final rush to assemble components for a bomb - and they express high confidence that it is still at least a year away from the capacity to build one and would then need more time to fit a warhead onto a missile. This contrasts with Netanyahu’s timetable, although he stopped short of saying Iran had decided to manufacture a weapon.Netanyahu showed no signs of backing off from his pressure campaign and equated the danger of a nuclear-armed Iran with the Islamist fury that fueled attacks on US embassies across the Muslim world last week.There have been no accusations, however, of any Iranian role stoking violence that hit Middle Eastern and African capitals.Speaking via satellite from Jerusalem, Netanyahu argued that a credible US ultimatum was needed to curb Iran, which denies it is seeking a nuclear bomb.“They’re in the ‘red zone,’” Netanyahu said, using an American football metaphor for when a team is close to scoring a touchdown. “You can’t let them cross that goal line.”Mohammad Al Jafari, commander-in-chief of Iran’s Revolutionary Guards, threatened retaliation for any Israeli attack, saying US bases in the region would be hit and trade via the Strait of Hormuz, a vital oil link, would be disrupted.“Nothing of Israel would remain,” he said.