Yahoo News reports that "Secretary of State John Kerry threatened Thursday to walk away from nuclear talks as he signaled that diplomats won't conclude an agreement with Iran over the coming hours — another delay that this time could complicate American efforts to quickly implement any deal."
"It was the strongest indication yet of U.S. frustration with Iran, and vice versa, coming two days after President Barack Obama vowed a similar response to Iranian intransigence and suggesting patience was running out as the current round of talks headed into its 14th day."
"Under U.S. law, the seven nations negotiating in Vienna have to complete the accord before the end of Thursday in Washington to avoid invoking a 60-day congressional review period during which President Barack Obama cannot waive sanctions on Iran. If they meet the target, the review would only be 30 days... The delay could imply that the U.S., Iran and other negotiating powers may end up having to push off the talks until September when any deal would again only amount to a 30-day review period."