Iran's foreign minister has expressed cautious optimism about upcoming talks on Iran's nuclear programme, saying the issue is "not insoluble".
World powers and Iran are due to meet in Geneva later on Thursday for a further round of discussions.
Foreign Minister Javad Zarif said the talks would be "highly laboured" but the aim was to "cross over the wall of distrust" created by Western policies.
The West suspects Iran of seeking to build nuclear weapons.
Tehran says its nuclear programme is for peaceful purposes.
In comments broadcast on Iranian TV on Thursday, Mr Zarif repeated Iran's long-standing assertion that to "refrain from seeking nuclear weapons is a policy of the Islamic Republic of Iran".
The two-day meetings in Geneva come after the two sides described last month's discussions on the issue as "substantive and forward-looking".
International negotiators said they were considering an Iranian proposal, although no details have been released.
The latest round of talks bring together Iranian officials and representatives of the "P5+1" - the permanent members of the UN Security Council (Britain, China, France, Russia and the US) plus Germany - also known as the E3+3.
Ahead of the meetings, a senior US administration official told reporters that Washington wanted Tehran to agree on a "first step" to stop advancing its programme further.
The official, who spoke on the condition of anonymity, said the US was hoping for "an initial understanding that stops Iran's nuclear programme from moving forward and rolls it back for the first time in decades".
Last month, the EU's top foreign policy official, Catherine Ashton, said the the P5+1 and Iran had "their most detailed talks ever".
Last month's talks were the first since Hassan Rouhani - seen as a relative moderate - became Iran's president in August.
International negotiators want Tehran to take specific steps to prevent it from ever being able to make nuclear weapons.
In return, they promise to lift some of the international sanctions imposed in recent years.
Key international demands include the acceptance by Iran of a comprehensive verification regime - with unannounced checks - and a reduction in Iran's level of uranium enrichment.
Iran subscribed to a fuller inspection regime under the International Atomic Energy Agency (IAEA), which was known as the additional protocol, until 2006.
Western nations have also been pressing for Tehran to halt the production and stockpiling of uranium enriched to 20% - a step away from achieving a nuclear weapons capability.
They also want Iran to send some of its stockpiles abroad, and shut down the Fordo production site near the city of Qom, where most of the higher-grade enrichment work is done.
Since 2006 the UN Security Council has imposed a series of sanctions - including asset freezes and travel bans - on entities and people involved in Iran's nuclear programme.
Separate US and EU sanctions have targeted Iran's energy and banking sectors, crippling its oil-based economy. Iran wants the sanctions lifted.