Negotiators from Iran and six world powers are meeting in Geneva Thursday in their latest bid to resolve a decade-long standoff over the Iranian nuclear program.
The two-day talks follow a meeting last month that both sides described as positive.
Iranian Foreign Minister Javad Zarif, who leads Iran's delegation, said Thursday he expected "serious" negotiations, and that a deal could be reach this week if both sides try their best.
He spoke after a breakfast meeting with European Union foreign policy chief Catherine Ashton, who serves at the chief negotiator for the group that includes the United States, Britain, China, France, Russia and Germany.
Iran is seeking relief from international sanctions, while the six nations want assurances that Iran is not trying to build nuclear weapons.
A senior U.S. official told reporters Wednesday that the international side is prepared to offer limited sanctions relief in exchange for Iran cutting back its uranium enrichment activity, but that any move could be canceled if Iran failed to comply.
The official said the two sides are beginning to understand what a "first step" in reaching an agreement could be.