26 September 2013 Last updated at 17:07 ET 
Mr Kerry (L) and Mr Zarif (R) met on the margins of the UN General Assembly in New York
The highest-level talks on Iran's nuclear programme for at least six years are taking place at the United Nations in New York.
US Secretary of State John Kerry is meeting Iranian Foreign Minister Mohammad Javad Zarif.
Diplomats from China, Russia, Britain, France and Germany are also there.
New Iranian President Hassan Rouhani has said he wants to reach a deal on the nuclear dispute in three to six months.
Continue reading the main story Analysis
James Reynolds BBC Iran correspondent
In recent years, the travelling brigade of nuclear negotiators has seen much of the world. Air miles aside, they have achieved almost nothing of substance. Diplomats have held talks in Geneva, Istanbul, Baghdad, Moscow, and Almaty. The most recent meeting was in Kazakhstan's biggest city in April 2013.
At times it has been hard to describe the nuclear talks as actual negotiations. More accurately, they have often resembled parallel monologues. But the P5+1 is meeting a new Iranian team.
Iran's newly appointed Foreign Minister, Mohammad Javad Zarif, replaces Saed Jalili as chief negotiator. Mr Zarif will report directly to Iran's President Hassan Rouhani - himself a former nuclear negotiator.
But the Americans have said there will be no major concessions until the Iranians take concrete steps to reassure the world they are not seeking nuclear weapons.
Iran reaches out Earlier, President Rouhani told the UN General Assembly that no country should possess nuclear arms.
Iran has been negotiating over the nuclear issue since 2006 with the P5+1 - the five permanent members of the UN Security Council, plus Germany.
Since Mr Rouhani's election in June, Iranian officials have reached out to the West, saying they want to address concerns over Iran's nuclear programme.
"We're not expecting any breakthrough in this initial meeting,'' said White House spokesman Jay Carney ahead of the talks.
"But this is part of us testing the seriousness of the Iranians, who are obviously engaging in new overtures and showing new interest in trying to solve this very serious matter."
On Tuesday, Mr Rouhani told the UN General Assembly that he was prepared to engage in "time-bound and results-oriented" talks.
On Thursday, he called for stricter controls on nuclear weapons as part of a global effort to eventually rid the world of them.
"No nation should possess nuclear weapons, since there are no right hands for these wrong weapons," he said, speaking on behalf of the Non-Aligned Movement at the General Assembly.
'Moderate course' 
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Hassan Rouhani: "The indefinite possession of nuclear weapons cannot be tolerated"
The P5+1 have asked Iran to halt production and stockpiling of uranium enriched to 20% - a step away from achieving a nuclear weapons capability.
They also demanded Iran shut down the Fordo underground enrichment facility.
In return, they offered to ease the sanctions that have severely affected Iran's economy.
President Obama has welcomed the new Iranian president's more "moderate course".
He told the UN on Tuesday that the US wanted to resolve the nuclear issue peacefully, but was determined to prevent Iran from developing a nuclear weapon.
Mr Rouhani has said he is fully empowered by Iran's Supreme Leader Ayatollah Khamenei to negotiate on the issue.
The BBC's Bridget Kendall, who is at the UN, says President Rouhani has signalled a sharp departure from the foreign policy and the tone of his predecessor, Mahmoud Ahmadinejad, whose bombastic pronouncements at the UN in the past resulted in walk-outs.
