Sanctions, inspections, and decision-makers: The number of things that could still trip up an Iranian nuclear agreement is small, but they're show-stoppers.

PARIS — After the most recent of many deadlines for the marathon Iran nuclear talks in Vienna came and went, one Iranian analyst with close ties to the negotiators suggested, "At this point it's a question of how much more they can take; there's a limit to how many schnitzels you can eat."

Well, now it looks like a deal is done—but not quite. The Associated Press reported Sunday that two diplomatic sources said an announcement was imminent—maybe Sunday, but more likely Monday. The document in question reportedly runs about 100 pages and "logistically" a deal tonight is said to be "simply impossible." So don't wait up.

The draft agreement mostly likely will be enough to get the negotiators home to Tehran, Washington, London, Paris, Beijing, Moscow and Berlin early this week. But it still won't be signed, sealed and delivered. And as U.S. Secretary of State John Kerry and Iranian Foreign Minister Javad Zarif head back to their respective capitals several issues loom ahead that bear close watching as critics on all sides prepare for attack. Republicans in the U.S. Congress already are dissing the document they have yet to see.

Before focusing on a few of the tricky details, there's one big question, though: If this deal fails, what's Plan B?

In the worst of all possible worlds (which often seems to be where we're headed these days), heavy sanctions would remain in force. Iran would take a hard line, pushing forward with more nuclear development and fewer, weaker, or no inspections, and once again the world very likely would be headed toward a major war in the Middle East with Israel leading the way lest its very survival be called into question by nuclear-armed mullahs. In such a fight, Washington would soon find itself with little choice but to join in.

"At this point it's a question of how much more they can take; there's a limit to how many schnitzels you can eat."

Or, perhaps, the world would muddle through with less apocalyptic scenarios. The allies who've been persuaded thus far to impose sanctions on Iran would start to peel away; the constraints on Iran's economy would fray; and as the pressure eased the Iranians would be careful not to cross any threshold that might actually start a war.  Even so, Iran would return solidly to the status of "nuclear threshold state" that it had achieved before the current talks began, positioned only a few months or weeks away from producing nuclear weapons if it chose to do so.