Sanaa (AsiaNews/Agencies) - Two days of talks between Iranian Foreign Minister Mohammed Javad Zarif with US Secretary of State John Kerry and senior EU envoy Catherine Ashton (pictured) have not reduced the "big gaps" that exist between Iran, the US and the EU over Tehran's nuclear programme with less than three weeks before the 24 November deadline.
After the talks ended on Monday, the US State Department said they had proven "tough, direct and serious" whilst adding "there is still time" for progress.
Iran's deputy foreign minister Abbas Araghchi said "no progress" had been made during the two days. "We can no longer talk about progress in the negotiations, but we are optimistic that we can reach an accord" before 24 November, the ISNA news agency quoted him as saying.
Privately, Iranian officials told Al Jazeera that an accord is not possible unless one or both sides make significant concessions they so far have rejected.
Likewise, "little progress" was made in nuclear talks, an Iranian official said, cited in Al Arabiya.
The key sticking point is the number and type of uranium-enriching centrifuges Iran would be allowed in exchange for sanctions relief and rigorous inspections of its nuclear sites.
The issue is part of the final destination of uranium, which for Tehran has purely civilian purposes, but for others, especially in Israel, could allow Iran to develop nuclear weapons.
Negotiations have become complicated by the fact that the Iranian nuclear issue has become entangled with the fight against the Sunni-centred Islamic State, Shia Iran's mortal enemy.
The shared interest in fighting and eliminating the latter has led to talk about possible agreements, secrets or otherwise, between the US and Iran.
In a secret letter last month to Iran's Supreme Leader Ali Khamenei, President Obama cited the two nations' shared interests in fighting Islamic State.
However, for the US president, cooperation and lifting of sanctions depend on reaching an agreement on the nuclear issue, which the new Republican majority in Congress appears unwilling to do.
An Iranian source said that Obama's recent letter to Iran's Supreme Leader had a "positive impact".
"These diplomatic correspondences have had a positive impact on Iran's top leadership and are essential in changing attitudes to reach an agreement, although the [latest] letter is solely concerned with mutual interests in combating the Islamic State of Iraq and Syria [ISIS]," Asharq Al-Awsat cited an adviser of Zarif as saying.