Critics have expressed suspicions about Iran's uranium enrichment, fearing that Iran may secretly be transforming nuclear fuel into atomic bomb-grade materials.
On Monday, Iran's Araqchi said shipping Iran's enriched uranium out of the country was a "red line." But on Wednesday, he hinted at flexibility, saying that "red lines need not be obstacles."
Iran insists the West must accept its right to enrich nuclear fuel for civilian purposes as allowed under the Treaty on the Non-Proliferation of Nuclear Weapons, to which Iran is a signatory.
This week's high-level talks in Geneva are the first such talks since the election of President Hassan Rouhani this summer raised the prospect of a shift in direction from Iran.
During a visit to the U.N. General Assembly in September, Rouhani's diplomatic approach raised hopes in the West of a thaw in relations with Tehran and progress in negotiations on its nuclear program.
Rouhani's visit culminated in a phone call with U.S. President Barack Obama and a meeting between U.S. Secretary of State John Kerry and Iran's Zarif.
It was the first such high-level contact between the two sworn enemies since Iran's 1979 revolution, which sent relations between the two into a deep freeze.
In another sign of easing tensions, Iran's state news agency IRNA reported Wednesday that Iran and Britain plan to introduce their nonresident charges d'affaires -- the level of diplomat below ambassador -- within two weeks.
Tehran and London agreed to the step on October 8, after a telephone call between Zarif and his British counterpart, William Hague. The diplomats' mission will be to improve relations on the way to the eventual reopening of embassies, Hague said then.
Asked about Wednesday's IRNA report, Britain's Foreign and Commonwealth Office told CNN that an announcement would be made in due course.
Britain closed its embassy in Iran and evacuated its entire diplomatic staff from that country in late 2011 after hundreds of student protesters stormed the embassy and another British diplomatic compound. Hague also ordered the Iranian Embassy in London to close immediately, saying that Iran was in breach of its international obligations to protect diplomatic missions.
Israel warns against easing sanctions
As the latest talks in Geneva continue, Israel has warned against easing the punishing economic sanctions imposed against Iran too soon.
Such a move would be a "historic mistake," Israeli Prime Minister Benjamin Netanyahu said Tuesday.
"Now is an opportune moment to reach a genuine diplomatic solution that peacefully ends Iran's military nuclear program," he said. "This opportunity can only be realized if the international community continues to place pressure on Iran, because it is that pressure that has brought Iran back to the negotiations in the first place."
Not everyone is pleased with the talks.
Alireza Jafarzadeh, with the opposition National Council of Resistance of Iran, accused Iran of using them to buy time to move forward with its nuclear weapons program. He called for still tighter sanctions.
"The P5+1 is allowing Iran to talk its way into a nuclear bomb; this explains the new atmospherics and smiles by the Iranian regime's officials," Jafarzadeh said. "The ruling mullahs only understand the language of strength and decisiveness. More concessions will only result in more deceit by the Iranian regime."
Ali Larijani, Iran's powerful parliamentary speaker and a close associate of the nation's supreme leader, Ayatollah Ali Khamenei, said last week that Iran is serious about resolving the dispute over its nuclear program.
It is keen to resolve the issue "in a short period of time," he told CNN's Christiane Amanpour in an exclusive interview from Geneva. "From Iran's side, I can say that we are ready," he said.