It doesn’t appear that this roadblock is going to actually prevent a deal, but diplomats say that the talks will continue into next week now before a deal can be reached.
That could be a major problem, with Congress up in arms about the deal (citing Israeli objections) and Rep. Ed Royce (R – CA) is planning to hold hearings on Wednesday, meaning those talks could wind up continuing in parallel with Congressional hearings meant explicitly to derail them.
Though officials wouldn’t confirm what the obstacle to the deal was, some rumors are that it surrounds the Arak heavy water reactor. The reactor is being constructed to replace the aging Tehran Research Reactor as a source of medical and industrial isotopes.
The US has complained that the reactor would produce plutonium as a waste product, though Iran hasn’t built any of the reprocessing facilities to try to recover such waste, and is reportedly willing to ship the waste abroad, as they are with the Bushehr reactor.