By Fredrik Dahl
VIENNA (Reuters) - Iran and six world powers held "substantive and useful" expert-level talks over Tehran's nuclear program this week, they said on Friday, ahead of a new round of political negotiations later this month.
Seeking to build on an interim agreement reached late last year in Geneva, Iran and the major powers aim to hammer out a final settlement of the decade-old dispute over the Islamic Republic's atomic activities by late July.
Both sides have made clear their political will to reach a long-term accord and have scheduled a series of meetings in the coming months. But they also acknowledge that there are still big differences over the future scope of Iran's nuclear program and that success is far from guaranteed.
The March 5-7 talks at the United Nations complex in Vienna, which ended around midday on Friday, were to prepare for the next meeting of chief negotiators due to start on March 18, also in the Austrian capital.
"The talks are very serious and substantive and useful," the head of the Iranian delegation at the expert-level talks, senior Foreign Ministry official Hamid Baidinejad, told Iran's Fars news agency ahead of Friday's session.
He later told the official IRNA news agency that "the result will be conveyed to capitals" but gave no details.
In Brussels, a spokeswoman for European Union foreign policy chief Catherine Ashton said: "I can confirm that the technical talks are over, they were substantive and useful."
Ashton is coordinating negotiations with Iran on behalf of the powers - the United States, France, Germany, Britain, Russia and China - and EU experts took part in the meeting.
Officials said experts from Russia also participated in the talks in Vienna, suggesting there was no immediate impact on the nuclear negotiations from the crisis in Ukraine.
A senior diplomat from one of the big powers said this week there had been "no suggestion by anyone" that the crisis would impede discussions on Iran or other issues such as Syria where the United States and Europe are trying to cooperate with Russia.
Western officials want Iran to significantly scale back its uranium enrichment activities to ensure that it would be unable to build a nuclear bomb quickly if it ever decided to do so.
Iran denies allegations that it is seeking the technical know-how and means to assemble nuclear weapons and says it will not shut any of its nuclear sites, which include the uranium enrichment plants at Natanz and Fordow and a planned heavy water reactor at Arak.
An official of Iran's atomic energy organization earlier this week said the negotiations would be "time-consuming".
"We want to continue our activities. Some on the other side have imaginary concerns about us veering from non-peaceful use (of nuclear energy). We are studying ways to remove that," Behrooz Kamalvandi told Iran's IRNA news agency on Wednesday.
Iran wants Western and U.N. sanctions that are severely hurting its oil-dependent economy to be lifted, having won limited relief in exchange for curbing its most sensitive nuclear work under the six-month Geneva deal, which took effect on January 20.
Uranium can be used to fuel a planned network of nuclear power plants, which is Iran's stated goal, but also provide fuel for bombs if processed to a high fissile concentration, which the West fears may be Iran's ultimate aim.
(Additional reporting by Parisa Hafezi in Ankara, Justyna Pawlak in Brussels and Lou Charbonneau at the United Nations in New York; editing by Andrew Roche)