Talks between Iran and the six world powers started on Tuesday in Almaty, Kazakhstan, after a nine-month break.
The Iranian delegation is headed by Saeid Jalili and the group of Britain, China, France, Germany, Russia and the United States is led by EU foreign policy chief Catherine Ashton.
Both sides seek a diplomatic solution to the dispute over Iran’s nuclear projects but sharp differences persist as both sides.
The five permanent UN Security Council members and Germany demand that Iran suspend 20-per-cent uranium enrichment, ship the already enriched uranium to a third country and close its new enrichment site of Fordo, south of Tehran.
In return, they would present a new offer to ease some of the sanctions imposed on Iran over its refusal to address concerns that it is trying to build a nuclear weapon.
Iran denies that it is developing a secret weapons programme, but demands recognition of its rights to pursue a civil nuclear programme and the lifting of all sanctions.
Tehran has ruled out closing the Fordo site but said it would be ready to compromise on other demands if its nuclear rights were acknowledged.