According to an American official who was involved, Tamir Pardo wanted to take the pulse of the Obama administration and determine what the consequences would be if Israel bombed Iranian nuclear sites over American objections. Pardo raised many questions, according to this source: “What is our posture on Iran? Are we ready to bomb? Would we [do so later]? What does it mean if [Israel] does it anyway?” As it is, Israel has stopped sharing a significant amount of information with Washington regarding its own military preparations…

In June Israeli intelligence and military officers stopped discussing any details of their planning, analysis, and training cycles for a possible attack on Iran. Until then cooperation had been close: a regular video teleconference between U.S. and Israeli national-security advisers to discuss Iran was established during the first Netanyahu visit to Washington, in 2009. As one senior Israeli official puts it, “We … both wanted no surprises.”

For about four months, however, the Israelis went mum. Meetings continued, but they weren’t substantive. “I knew they were upset; when they stopped talking, we said, ‘We got a problem,’?” a senior U.S. intelligence official tells Newsweek. (This was confirmed by a military officer working on the Iran file.) The blackout was mostly lifted by Israel in October. But by that time the Obama administration had already been spooked, and with good reason: it’s possible that Israel could start a war with Iran that the United States would be compelled to finish. (As it is, Israel continues to withhold a “top layer of information” regarding Iran, says the U.S. intelligence official.)…

The key question now is how much time is left to achieve a negotiated solution. Israeli officials say that the United States thinks it can afford to wait until Iran is on the very verge of weaponizing, because U.S. forces have the capacity to carry out multiple bombing sorties and cripple the Iranian program at that point. Israel, however, would not be able to carry out such a sustained attack and would need to hit much sooner to be effective—before Iran could shelter much of its program deep underground. One former Israeli official tells Newsweek he heard this explanation directly from Defense Minister Ehud Barak. “If Israel will miss its last opportunity [to attack], then we will have to lean only on the United States, and if the United States decides not to attack, then we will face an Iran with a bomb,” says the former Israeli official. This source says that Israel has asked Obama for assurances that if sanctions fail, he will use force against Iran. Obama’s refusal to provide that assurance has helped shape Israel’s posture: a refusal to promise restraint, or even to give the United States advance notice.