By Steve Gutterman
MOSCOW (Reuters) - Russia said on Thursday that Iran and six global powers made progress in expert-level talks this week on the standoff over Tehran's nuclear programme but there was no breakthrough and that backsliding remained a danger.
"This progress is real but it is not sufficient to speak of a definitive shift," Deputy Foreign Minister Sergei Ryabkov, Russia's chief negotiator on the issue, said of the talks in Istanbul on Monday.
"We cannot say this progress is irreversible. This alarms us a little, but from round to round, we have a more and more businesslike discussion of all the issues," he told reporters.
Russia, the United States, Britain, France, Germany and China are spearheading diplomacy meant to ensure that Iran, which says its nuclear programme has purely peaceful ends, neither seeks nor achieves nuclear weapons capability.
In Istanbul, the six powers gave Iran more details of proposals made at political-level talks in late February in the Kazakh city of Almaty, where they offered Tehran modest sanctions relief if it curbs its most sensitive nuclear work.
Ryabkov said the sides had "plenty of homework to do" before the next meeting at a political level, in Almaty on April 5-6, but suggested the technical talks had laid some good groundwork.
"When there is movement in talks, you do your homework in a good mood, and not like a failing student who is about to get kicked out of the classroom anyway," he said.
"It was a very useful event, ending on a positive note," said Ryabkov, who welcomed what he called "Iran's display of readiness to conduct concrete dialogue."
Russia, which built Iran's first nuclear power plant and has better relations with Tehran than do Western powers, has tended to be more upbeat than Western leaders about Iran's attitude toward the negotiations.
Western officials have said the offer presented by the six powers in Kazakhstan included an easing of a ban on trade in gold and other precious metals, and a relaxation of an import embargo on Iranian petrochemical products.
In exchange, a senior U.S. official said, Iran would among other things have to suspend uranium enrichment to a fissile concentration of 20 percent at its Fordow underground facility and "constrain the ability to quickly resume operations there".
Iran has hinted it is not satisfied with the powers' offer, although chief negotiator Saeed Jalili said after last month's Almaty talks that the six had tried to "get closer to our viewpoint" and that, he added, was positive in itself.
Western diplomatic sources said experts had engaged in detailed technical talks about the powers' proposal in the Istanbul meeting, but it was unclear whether this would lead to substantive results at the political talks in early April.
The European Union, whose foreign policy chief Catherine Ashton oversees contacts with Iran for the six powers, has given no public indication of whether there was progress in Istanbul.
Russia went along with four rounds of U.N. Security Council sanctions against Iran over its nuclear programme but opposes further sanctions and has sharply criticised separate Western sanctions, saying they are counterproductive.
(Additional reporting by Fredrik Dahl in Vienna; Editing by Mark Heinrich)