U.S. threatens to quit nuclear talks, as Iran blames West for divide

U.S. Secretary of State John Kerry threatened Thursday to walk away from nuclear talks as he signalled 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. The Iranians immediately fired back, accusing the U.S. and its European allies of causing the deadlock.

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Kerry and other Western officials said Iran still hadn't made the tough political decision to roll back its nuclear program. But a senior Iranian official said it was the Americans and their partners who were backtracking on several key commitments related to Iran's permitted level of nuclear activity and definitively ending economic sanctions against Tehran.

"This is not open-ended," Kerry told reporters outside the 19th-Century Viennese palace hosting the negotiations. "We can't wait forever for the decision to be made. If the tough decisions don't get made, we are absolutely prepared to call an end to this process."

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.

Significant delay

Thursday's latest delay for a comprehensive deal is significant. Iran is demanding prompt easing of economic penalties for nuclear concessions, and the longer it takes world powers to make good on their promises, the longer they'll have to wait for the Iranians to scale back their nuclear program.

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 Obama cannot waive sanctions on Iran. If they meet the target, the review would only be 30 days.

The spectre of prolonged public relations campaigns for and against the pact also may not work in Obama's favor. 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.

"We will not let ourselves be rushed through any aspect of this," Kerry said. "If we are able to reach a deal, it has to be one that is able to withstand the test of time."

He acknowledged that the work of hammering out a deal was "incredibly technical" and the stakes "very high" but said the reason negotiators were still in Vienna despite having missed two previous deadlines for reaching an agreement was because they were "making real progress."

"We would not be here continuing to negotiate just for the sake of negotiating," he said. "We're here because we believe we are making real progress toward a comprehensive deal."

But he warned that even though some "tough issues" remain unresolved, one way or another, decisions "must be taken very soon."

"As I have said many times, we are not going to sit at the negotiating table forever, but we also recognize that we shouldn't get up and leave simply because the clock strikes midnight," he said ahead of the midnight Thursday deadline.

We will not let ourselves be rushed through any aspect of this.- John Kerry, U.S. secretary of state

Kerry spoke after discussing the state-of-play with other world powers for almost an hour Thursday evening. That conversation followed a flurry of other closed-door meetings, including a 45-minute session between Kerry and his Iranian counterpart.

"We're working hard, but not rushed, to get the job done," Iran's Foreign Minister Mohammad Javad Zarif tweeted. 

Iran says U.S. "obsessed" with sanctions

A senior Iranian official, who briefed foreign reporters covering the talks on condition no one quote him by name, declared the West's reluctance to ease economic penalties the biggest obstacle. The U.S. is "obsessed" with sanctions, said the official, adding that the deadlock could prove a major setback.

Russia's Foreign Minister Sergey Lavrov took Tehran's side.

"Our Western partners, who did not support a draft resolution entirely acceptable to the other parties, are at fault, not Iran," he tweeted.

French Foreign Minister Laurent Fabius said he would remain in Austria's capital for negotiations into Friday morning, citing "good things, but there is still work to do."

However, U.S. Energy Secretary Ernest Moniz, who has been leading the American negotiating team alongside Kerry, was to leave for Portugal for most of Friday to discuss climate change matters with the president, prime minister and other senior officials.

Iran prepares for post-sanctions era

As the talks continued, Iran's president, Hassan Rouhani, said his nation was preparing for a "post-sanctions" era, suggesting that a deal may be in sight to curb the Iranian nuclear program in exchange for the lifting of economic sanctions. His foreign minister, meanwhile, opined on Twitter that "with mutual respect, anything possible."

Later he was more cautious, saying "we're working hard but not rushed to get the job done."

U.S. won't accept bad deal

Kerry, nursing a broken leg, has been in Vienna since June 26 while Iran's Zarif has made one short trip to Tehran for consultations. Other foreign ministers have come and gone, however all but the top diplomats from Russia and China were present at Thursday's meetings.

When the talks missed their second deadline it raised new questions about the ability of world powers to cut off all Iranian pathways to nuclear weapons through diplomacy. Federica Mogherini, the European Union's foreign policy chief, spoke of "tense" moments, and the State Department extended the current interim nuclear arrangement with Tehran through Friday.

And new difficulties also have surfaced over the past few days. Iran is pushing for an end to a UN arms embargo on the country but Washington opposes that demand.

Obama has said the United States would walk away from the negotiating table rather than sign a bad deal.