Update

A number of sources (Economic Times, CNS News, ABC News) have provided a similar update as the current round of talks enter their 13th (and final?) day:

"US Secretary of State Kerry . . . has been in Vienna since 26 June, while Iranian Foreign Minister Zarif has made a short trip to Tehran [for a consult].  Other foreign ministers have come and gone, however all but the top diplomats from Russia and China were expected to be present at Thursday's meetings."  [The latter two are at the BRIC Summit in Ufa, Russia.]  Also, "on Wednesday US Energy Secretary Moniz met with Iranian nuclear cheif Ali Akbar Salehi for more than three hours, indicating that problems remained that only technicians can solve."  The rest is rehash of previously reported tidbits:

• Iran's President was preparing for a "post-sanctions" era, suggesting a deal might be in sight.
• President Obama conferred with the US negotiating team via secure video conference to provide guidance
• If the talks are approved after Thursday, Congress will have two months to review the accord, vice one if the deal is made by Thursday.
• Secretary Kerry "has been in Vienna since 26 June, while Iran's Foreign Minister Mohammad Javad Zarif has made a short trip to Tehran for consultations.  Other foreign ministers have come & gone, however all but the top diplomats from Russian and China were expected to be present at Thursday's meetings."  
• "On Wednesday, US Energy Secretary Ernest Moniz met with Iranian nuclear chief Ali Akbar Salehi for more than three hours, indicating problems remained that only technicians could solve."
• Iran's Zarif: With mutual respect anything is possible
• US (White House): We'll walk away if we don't have a good deal
• US Repubicans, as well as Israel & Saudi Arabia, remain skeptical

The NYT (Gordon) adds the political dimension as to the extended push, and why today is so important: "

“It is pretty darn hard for the Iranians to go home and deal with the politics in Iran,” said the official, who spoke on the condition of anonymity under the ground rules for the briefing. “Everyone understands that once we leave here, we are in less control of what happens in this negotiation. It gets more complicated, not less complicated.”

Also, some more details: "As Mr. Moniz and Mr. Salehi tried to resolve the final issues on Thursday morning, Federica Mogherini, the foreign policy chief for the European Union, convened a separate session with Mr. Kerry and senior diplomats from Britain, China, France, Germany and Russia, the five other world powers that are taking part in the negotiations with Iran."

The deadline is midnight Thursday (2pm EDT).