As nuclear talks enter what U.S. officials have described as the "final moment," Iran struck a defiant tone Friday, marking the forty-third anniversary of the Islamic Revolution that brought to power its hardline government.
In the streets of Tehran, thousands celebrated in convoys of cars and motorbikes because of COVID-19 restrictions -- waving flags, honking horns, and displaying "Down with U.S.A." signs.
MORE: Nuclear negotiations with Iran resumeBut elsewhere across the capital, a weary Iranian public suffering under years of tight U.S. sanctions and economic mismanagement are eager for relief, especially from sky-high inflation, which now exceeds 40%.
Whether they'll see a significant reprieve soon depends on the diplomatic efforts underway in Austria, where the U.S. and Iran are negotiating through proxies in an attempt to resuscitate a President Barack Obama-era nuclear deal.
At its core, the 2015 agreement saw the U.S. and international community lift certain sanctions on Iran in exchange for limits on its nuclear program -- a swap that was disrupted by former President Donald Trump when he exited the deal and reimposed crushing U.S. sanctions in 2018 -- an attempt to strengthen his hand in negotiations.
But in response, Iran has since then escalated its nuclear program, enriching enough uranium at high-enough levels that U.S. officials say they are just "weeks" away from having enough for a nuclear bomb.
One week ago, President Joe Biden's administration waived sanctions related to Iran's civilian nuclear program, exempting foreign countries and companies that work with Tehran on nonproliferation projects from penalties.
The move is aimed at laying the groundwork for resuming U.S. compliance with the 2015 deal, but Iran's foreign ministry called it "insufficient," with its president dismissive of the ongoing talks in the Austrian capital.
"We put our hopes on the east, west, north, south of our country and never have any hope in Vienna and New York," Iranian President Ebrahim Raisi said in a speech Friday.
Raisi's speech was repeatedly interrupted by chants of "Death to America" -- a familiar slogan that dates back to the 1979 revolution that toppled the U.S.-backed ruler and ushered in an Islamist government, led by a supreme leader known by the clerical title, ayatollah.
But for the thousands of Iranians joining the protests and burning flags, there are thousands more who lament the economic situation, desperate for relief.
"The high prices are really hurting us," one woman out shopping with her mother told ABC News. She declined to identify herself.
"I'm not that much into politics. I like my country, but the only problem is that things are really expensive, and when we have problems, states people do not really solve them," she said, adding that since Raisi was inaugurated in August, "Nothing has changed. Nothing has gotten better. Things are even getting worse after him."
Omid Kalavi, a toymaker in Tehran, said inflation has meant more people come to him for repairs than to purchase new toys for their children.
"I'm not a politician, but as far as I know, people are those who suffer the most from the political games. I can't say our government or the United States because of imposing sanctions -- I don't know exactly to be honest, but as far as I know, people are suffering from it most."
MORE: 'End game': Iran nuclear talks nearing resolution or nuclear crisis, US warnsWithout a deal, that economic hardship will continue. A senior State Department official said the U.S. would "fortify our response" if it has to walk away from talks, "and that means more pressure -- economic, diplomatic, and otherwise."
The Biden administration's efforts to negotiate a mutual return to the deal have not yielded results in 10 months of talks. When the two sides were making progress last June, the talks went on hiatus for Iran's presidential elections.
Raisi's government stalled for months before resuming negotiations in late November. After making hardline demands at the start of the new round of talks, they returned last month "in a serious, business-like negotiation," the senior State Department official said.
But time is running out to reach a new agreement. U.S. Special Envoy to Iran Rob Malley and other senior administration officials briefed Capitol Hill Wednesday on Iran's growing nuclear stockpile and the urgency of talks, which lawmakers described as "sobering" and "shocking."
"Breakout time has gone from a year to a matter of weeks," said Sen. Chris Murphy, D-Conn., echoing what Secretary of State Antony Blinken and other officials have said in recent weeks. Murphy added that "a deal is in sight, but there is significant gaps between the two sides that need to be closed."
The senior State Department official declined to discuss how much distance remains between both sides, saying nothing was agreed until everything was agreed. But Iran has demanded some sort of guarantee that a future U.S. administration cannot again exit the deal -- the kind of promise any American president can't give -- while also publicly calling for the U.S. to completely lift sanctions first.
On the other side, the U.S. has warned that Tehran's nuclear stockpile must return to the deal's levels -- enriching uranium to 3.67% and with a stockpile of 300 kilograms for the first 15 years of the deal.
"If is not reached ... in the coming weeks, Iran's ongoing nuclear advances will make it impossible for us to return to the JCPOA," White House press secretary Jen Psaki said Wednesday, using an acronym for the deal's formal name, the Joint Comprehensive Plan of Action.
But many critics say that point has already passed. Iran is spinning more advanced centrifuges and building more of them, enriching uranium metal, and enriching uranium up to 60% purity -- a short technical step from weapons-grade, which is above 90%.
Some analysts say the scientific knowledge Iran has developed since the deal was scrapped will be impossible to eliminate.
"You cannot put the genie back into the bottle. Once you know how to do stuff, you know, and the only way to check this is through verification," Rafael Grossi, director-general of the International Atomic Energy Agency -- the U.N. nuclear watchdog -- told the Financial Times last year.
But restoring the deal is intended to allow for that verification, ensuring Iran does not use its program to develop a nuclear weapon. Iran has obstructed the IAEA's work repeatedly in recent years. It has failed to account for uranium detected at three undeclared sites, and for a year now, it has barred the agency from reviewing data from surveillance equipment at Iran's declared sites.
The obstruction, which also includes harassing some IAEA inspectors, "was seriously affecting the ability of the Agency to provide assurance of the peaceful nature of Iran's nuclear program," the IAEA reported in late November.