Iran and world powers have agreed to meet next month to discuss Tehran's controversial nuclear programme after a day of talks in Turkey.
Catherine Ashton, the EU's foreign policy chief who has headed negotiations for the six international powers, said they had arranged to meet the Iranian delegation again in Baghdad on 23 May.
Saeed Jalili, Iran's chief negotiator, said there had been differences of opinion but that some important points had been agreed and that the next talks should focus on arranging measures to build mutual confidence.
Iran has been hit by new waves of Western economic sanctions this year.
Western participants had said previously that agreeing to meet for a second round of talks would constitute a successful day. It may remove some heat from a crisis in which warnings from Israel of a possible strike against Iranian facilities have stoked fears of a major war in an already unsettled Middle East.
After a day in which diplomats had spoken of a more engaged tone from Iranian officials compared to the 15 months of angry rhetoric on either side that has filled the hiatus since the last meetings, Ms Ashton called the talks useful and constructive.
"We want now to move to a sustained process of dialogue," Ms Ashton told a news conference, saying negotiators would take a "step-by-step" approach.
"The discussion on the Iranian nuclear issue have been constructive and useful," she said. "We want now to move to a sustained process of serious dialogue, where we can take urgent, practical steps to build confidence."
The six world powers present were the five permanent members of the United Nations Security Council - Russia, China, the US, France and Britain - plus Germany.
One non-Iranian diplomat called the atmosphere "completely different" from that of previous meetings, as Western delegates watched out for signs that Iran was ready to engage after more than a year of threats in defence of its right to pursue nuclear energy and denials it wants to be able to build an atom bomb.
Ms Ashton told reporters in Istanbul that the negotiating powers wanted Iran to meet international obligations - it is a signatory to the treaty which prevents the spread of nuclear weapons - and should reciprocate in negotiations.
The West accuses Iran of trying to develop a nuclear weapons capability. Israel - believed to be the only Middle East state with an atomic arsenal - sees Iran's atomic plans as a threat to its existence and has threatened military action.
Iran says its programme is peaceful and has threatened to retaliate for any attack by closing a major oil shipping route.
The US and Israel have not ruled out military action to destroy Iran's nuclear sites.
