Tony Karon writes: ‘I believe there is a window of time to solve this diplomatically but that window is closing,” President Barack Obama said last week about the nuclear standoff with Iran. The “window closing” phrase was then echoed on Friday by Secretary of State Hillary Clinton, who insisted: “We are determined to prevent Iran from obtaining a nuclear weapon.”

But hang on a minute. Three weeks ago, Mr Obama warned that he would take military action if it became necessary to stop Iran from acquiring a nuclear weapon. But in the same breath, he pointed out that Iran was not building a nuclear weapon, and had not in fact taken a decision to do so despite steadily amassing infrastructure that would enable it. Mr Obama quoted approvingly from a recent speech in which Supreme Leader Ayatollah Ali Khamenei reiterated his long-standing fatwa declaring that the construction, stockpiling and use of nuclear weapons was a “sin against Islam”.

So, if Mr Obama himself has emphasised that Iran is not moving towards his trip-line for military action, unless there’s been a qualitative shift towards weaponisation in Iran’s nuclear work in the past three weeks, who is closing the metaphorical “window” for diplomacy?

There may be three related elements at work. First, there is Israel threatening unilateral military action based on its own red lines and on its own timetable unless Iran yields. Then there’s the fact that Mr Obama’s Iran strategy was designed by Dennis Ross, who has since returned to his old job at a think tank created by the pro-Israel lobby Aipac. Mr Ross believes the only way to achieve diplomatic results with Iran is to pin it in a chokehold of sanctions, and make it believe worse is to come.

And then there’s Mr Obama’s concern with securing his re-election in November, which requires tough-guy posturing on Iran to counter charges from his Republican opponents, egged on by Israel’s alarmism, about being “weak” in the face of an Iranian “danger”.