'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".
As Jerusalem Post columnist and former Aipac lobbyist Douglas Bloomfield noted this week: "Netanyahu reportedly feels he has Obama boxed in ... in the months before the November election, the president will have no choice but to back up an Israeli attack however ill advised or opposed because failure to do so would look like abandoning our close ally in its hour of need."
Whether he intended to or not, Bloomfield also offered Mr Obama a reason to be highly sceptical of Mr Netanyahu's agenda in the months ahead: "It's no secret," wrote the longtime lobbyist, "that one of Netanyahu's objectives is to help defeat the incumbent because Obama in a second term might not be so easily bullied."
For all the hype, Israel remains unlikely to bomb Iran before November. Mr Netanyahu is a cautious politician, and he's being told by his military and intelligence chiefs that starting a war with Iran on the basis of the status quo would be a mistake.
It's no secret, also, that Mr Obama and the US military strongly oppose starting a war of choice with Iran. Mr Obama, and his fellow western leaders who share his fear, need the Istanbul talks to succeed at least as much as the Iranians do. And there's no reason to believe Iran is coming to the table bearing a white flag.
Tehran may well be ready to offer some sort of confidence-building deal based on suspension of its higher, 20 per cent enrichment of uranium and even shipping out some of the stockpile of that material. But if so, it will expect a quid pro quo in easing of sanctions, which would expose Mr Obama to political risk at home, fuelled by pressure from Israel.
Israel's bottom lines, of course, are not the same as Mr Obama's: Israeli hawks insist that Iran can't be allowed to have the means to build a nuclear weapon, by which they mean that it can't be allowed to retain even civilian enrichment capability.
And Mr Ross this week published a Washington Post opinion article urging the Obama administration to give Israel greater influence over the US negotiating position. "Because Israel is the only country that Iran has repeatedly threatened to 'wipe off the map'," Mr Ross wrote, "it is reasonable for it to have some input into the objectives of diplomacy and the timetable for progress in negotiations. The more Israelis feel their views are being taken into account, the more inclined they will be to give diplomacy a chance to work before resorting to force."
But Israel's bottom line that Iran can't be allowed to enrich uranium even under tougher scrutiny is a sure-fire deal killer, and allowing it to set the terms of diplomacy is a recipe for failure. Indeed, former Mossad chief Efraim Halevy warned last week that Israel's government is not as supportive as it ought to be of the effort to find a diplomatic solution. He also warned that achieving a deal requires understanding the concerns that drive Iran's leaders, and finding ways to address those without paying an exorbitant price.
Plainly, sanctions and threats are not going to be enough to change the game.
A diplomatic "solution", of course, is months or even years away, and would require a sea-change in relations between Iran and the West. So the best that can be hoped for in Istanbul, in fact, is that the sides agree to steps that could start a process of mutual confidence-building - a process that would hardly be likely to produce a final result before Americans vote in November, but that may be substantial to keep that proverbial closing window jammed open at least into next year.
Tony Karon is an analyst based in New York
On Twitter: @TonyKaron