The official, speaking on condition of anonymity, added that extending the deadline “would be absolutely the worst scenario,” citing fears over reactions from hardliners in both countries.
The source said that extending the talks may also result in Republicans in the US Congress, who won the majority of seats in the recent mid-term elections and oppose negotiations with Iran, undermining a potential deal with Tehran.
After meeting the former European Union representative Catherine Ashton in Vienna on Tuesday, Iran’s Foreign Minister Mohammad Javad Zarif warned that his government will not accept “excessive” Western demands, underscoring obstacles hampering a historic deal ahead of this month’s deadline.
“The talks with Ashton were good and reaching a deal depends on the political will of the other side,” state-run IRNA news agency quoted the foreign minister as saying.
The US Secretary of State John Kerry described the period ahead of the deadline as being “very critical.”
“It’s imperative, obviously, that Iran work with us in all possible efforts to prove to the world the program is peaceful,” Kerry said during a visit to London.
The six world powers—France, China, Germany, Russia, US and Britain—insist that Iran should reduce its uranium enrichment capacity and the number of operational centrifuges, to make it harder for Iran to divert any nuclear material to an atomic weapons program, and easier to detect if Tehran does so.
Tehran, on the other hand, says its enrichment activities are meant to produce fuel for nuclear power plants, in what it claims is its sovereign right as a signatory to the Nuclear Non-Proliferation Treaty.
On arriving to the Austrian capital Zarif said: “We are here to find a solution that respects the Iranian nation’s rights and removes the legitimate concerns of the international community.”
In comments to Asharq Al-Awsat, analyst Ali Vaez of the International Crisis Group said current international circumstances and the political changes in Washington make it necessary for the two sides to reach a deal as soon as possible.
Iran needs to make sure how far the international community will commit to any potential deal in exchange for allowing the International Energy Agency (IEA) to monitor its enrichment activity, he said.
Iran, for example, expected trade in some foods and agricultural products to resume after the Geneva talks, but they have remained in place due to manufacturers’ fears over the future of sanctions on Iran, Vaez said.