The trilateral meeting that among the US, Iran and the European Union(EU) in Muscat, capital of Oman, ended Monday with little progress.
The two-day meeting, attended by US Secretary of State John Kerry, Iranian Foreign Minister Mohammad-Javad Zarif and EU adviser Catherine Ashton, comes just two weeks before the Nov 24 deadline for a comprehensive deal on Iran's controversial nuclear programme, Xinhua reported.
The Western sanctions against Iran and the country's uranium enrichment capacity are now the two key issues of the tough negotiations.
After the meeting, an Iranian official told reporters that little progress was made after the talks, and gaps still remain over the core issues.
The meeting is part of the EU-coordinated negotiations between Iran and the P5+1 group, which include Great Britain, China, France, Russia, the US, as well as Germany.
Iran and the P5+1 group will hold another round of nuclear talks in Muscat Tuesday, Omani officials said.
In an interview aired Sunday on CBS News, US President Barack Obama said a "big gap" remains on how the West can have "verifiable, lock-tight assurances" Iran cannot obtain a nuclear weapon.
Prior to the Muscat meetings, IRNA news agency quoted Iran's senior nuclear negotiator Abbas Arachi as saying that the nuclear talks in Oman between Iran and the world powers are not likely to result in an agreement.
But he said reaching a final deal with powers over Iran's nuclear issue is "not difficult" before the Nov 24 deadline.
The meetings in Muscat also follow media reports that US President Barack Obama has written to Iran's Supreme Leader Ayatollah Ali Khamenei, expressing a "shared interest" in fighting the Islamic State(IS) extremist group in Iraq and Syria.
After the deal between Iran and the P5+1 group Nov 24 last year, both sides have held several rounds of talks, trying to work out a final agreement.
Under the interim deal agreed in Geneva in November last year, Iran agreed to suspend some sensitive nuclear activities in exchange for a limited sanction relief within 12 months to buy time for the diplomatic efforts.
The West wants Iran to significantly scale back its nuclear programme to address its concerns for proliferation risk, while Iran insists that its nuclear right is inalienable.
