Iran offered mixed signals Thursday as a deadline loomed in talks over Tehran's tattered nuclear deal with world powers, with the Iranian president defending the negotiations while the country's top diplomat and a security official blamed the United States for the deadlock.

The monthslong, indirect talks in Vienna have sought to both get U.S. to return to the accord that Washington unilaterally withdrew from in 2018, and have Iran restore limits on its rapidly advancing nuclear program.

Western diplomats have in recent days signaled the talks had reached their conclusion, laying the final decision with Iran. Ali Shamkhani, the secretary of the country's powerful Supreme National Security Council, wrote on Twitter early Thursday, trying instead to blame America for the deadlock.

The "U.S. approach to Iran’s principled demands, coupled with its unreasonable offers and unjustified pressure to hastily reach an agreement, show that U.S. isn’t interested in a strong deal that would satisfy both parties," Shamkhani wrote in multiple languages. "Absent U.S. political decision, the talks get knottier by the hour."

Shamkhani and other Iranian officials have repeatedly projected Western complaints about the Islamic Republic's behavior throughout the negotiations back to the West.

Speaking at a press conference in Vienna late Thursday, Rafael Mariano Grossi, the head of the International Atomic Energy Agency, was very tight-lipped.

"It’s no secret that these negotiations – which are not my negotiations, we (the IAEA) are participating and being consulted – that these negotiations are coming to a decisive point," Grossi said.

Iran's Foreign Minister Hossein Amirabdollahian spoke Thursday with European Union foreign policy chief Josep Borrell – and also criticized America for what he described as conveying "a new and different message to us every day through a coordinator."

"If the American side has a public opinion problem, I must say that we also have a public opinion problem in Iran," Amirabdollahian said, according to a Foreign Ministry statement. "They monitor developments with great sensitivity and precision and demand that the government respond to and effectively lift sanctions and maintain a peaceful nuclear capability."

However, Amirabdollahian added: "If realism governs the behavior of all parties, we are still close to reaching a good and strong agreement."

Earlier, hard-line President Ebrahim Raisi's Twitter account appeared to offer Iran's theocracy cover for potentially supporting a possible deal in Vienna.

"The government is doing negotiations in the way of the supreme leader’s framework and has not and will not retreat from any red lines (that) were announced," he wrote.

'Window closing' to reach Iran nuclear deal

France's foreign ministry said Thursday that the opportunity to reach a deal on reviving the 2015 nuclear accord between Iran and world powers was closing and called on all sides to take a responsible approach to reach an agreement.

"We are very close to an agreement, but the window of opportunity is closing," Foreign ministry spokesperson Anne-Claire Legendre told reporters in a daily briefing.

"We are concerned about the risks that additional delays pose to the possibility of concluding. Together with our E3 partners, we call on all parties to take a responsible approach and make the decisions necessary to conclude this agreement."

Iran’s civilian government operates on a narrow bandwidth under Supreme Leader Ayatollah Ali Khamenei, who has the final say on all matters of state. However, divisions exist within even the hard-line camp of Iran's theocracy – particularly on the nuclear deal and any interactions with the West.

Khamenei himself also offered rare yet vague remarks about the talks Thursday, vowing that restrictions on Iran’s ballistic missiles program, nuclear scientific progress and regional military policies remain non-negotiable.

In a speech to Iran's Assembly of Experts, Khamenei said there is no one "more naive and clumsy than those who suggest the reduction of the defensive power" of Iran.

"None of these arms of national power should be cut off," Khamenei added. He warned that without its military capabilities and nuclear progress, Iran would face "great dangers" and "a blow to its national power."

However, he said nothing directly about the looming deadline to restore the nuclear deal.

Russia's ambassador in the Vienna talks, Mikhail Ulyanov, told journalists in Vienna on Wednesday that "maybe it will be finalized tomorrow, maybe – but it's not for sure." Iran's top negotiator Ali Bagheri Kani rejoined the talks Wednesday after a quick trip back to Tehran for consultations and met with EU negotiator Enrique Mora.

Mora this week seemed to suggest whether the talks succeeded or failed now rested with the Islamic Republic.

"There are no longer 'expert-level talks.' Nor ‘formal meetings,'" Mora wrote on Twitter, responding to comments by an Iranian analyst. "It is time, in the next few days, for political decisions to end the #ViennaTalks. The rest is noise."

Mora’s comments mirror those of British and French negotiators. The latest wrinkle, however, is a demand Saturday from Russian Foreign Minister Sergey Lavrov that Blinken offers written guarantees over Moscow’s ability to continue trade with Iran as it faces sanctions over its war on Ukraine.

Meanwhile, amid the talks, Iran's paramilitary Revolutionary Guard announced Tuesday it had launched a second reconnaissance satellite into space. While not directly acknowledging the launch, a space object catalogue maintained by the U.S. military now lists the Noor-2 satellite as having been launched Tuesday by Iran. Its telemetry shows it in a stable orbit some 500 kilometers (310 miles) above the Earth's surface.

"No sanctions or restrictions can stop the great nation of Iran from developing," Amirabdollahian tweeted.