Iranian state media reported the comments by Ali Bagheri, Iran's top nuclear negotiator, and Mohammed Eslami, the country's civilian nuclear chief. It remained unclear, however, whether this represented an opening gambit by Iran's new hard-line president or signalled serious trouble for those hoping to restore the 2015 deal that saw Tehran strictly limit its enrichment of uranium in exchange for the lifting of economic sanctions.

The United States left the deal under then-President Donald Trump's “maximum pressure” campaign against Tehran in 2018. Since the deal's collapse, Iran now enriches small amounts of uranium up to 60% purity — a short step from weapons-grade levels of 90%. Iran also spins advanced centrifuges barred by the accord, and its uranium stockpile now far exceeds the accord's limits.

Speaking to Iranian state television, Bagheri referred to the previous rounds of talks only as a “draft”. “Drafts are subject to negotiation. Therefore nothing is agreed on unless everything has been agreed on,” he said. "On that basis, all discussions that took place in the six rounds are summarised and are subject to negotiations. This was admitted by all parties in today's meeting as well.”

Another state TV segment saw Bagheri in Vienna also saying Iran demanded a “guarantee by American not to impose new sanctions” or not re-impose previously lifted sanctions.

Eslami, speaking to Iran's state-run IRNA news agency, reiterated that demand.

“The talks (in Vienna) are about return of the US to the deal and they have to lift all sanctions and this should be in practice and verifiable,” he said.

Talks in Vienna resumed Monday after an over five-month hiatus as hard-line President Ebrahim Raisi took power. Raisi, a protege of Supreme Leader Ayatollah Ali Khamenei, campaigned on getting sanctions lifted. However, fellow hard-liners within Iran's theocracy long have criticised the nuclear deal as giving too much away to the West.

Iran's comments Tuesday stood in stark contrast to the optimistic tone offered by the European Union diplomat leading the talks.

“I feel positive that we can be doing important things for the next weeks,” Enrique Mora told reporters on Monday

Israel, Iran's regional, nuclear-armed rival, kept up its own pressure amid the negotiations. Israeli Prime Minister Naftali Bennett, in a video address delivered to nations negotiating in Vienna, warned that he saw Iran trying to “end sanctions in exchange for almost nothing”.

“Iran deserves no rewards, no bargain deals and no sanctions relief in return for their brutality,” Bennett said in the video that he later posted to Twitter. “I call upon our allies around the world: Do not give in to Iran's nuclear blackmail.”

Iran maintains its atomic programme is peaceful. However, US intelligence agencies and international inspectors say Iran had an organised nuclear weapons program up until 2003. Nonproliferation experts fear the brinkmanship could push Tehran toward even more extreme measures to try to force the West to lift sanctions.

Making matters more difficult, United Nations nuclear inspectors remain unable to fully monitor Iran's programme after Tehran limited their access. A trip to Iran last week by the head of the International Atomic Energy Agency, Rafael Grossi, failed to make any progress on that issue.?