London: Key talks involving six major countries and Iran on Tehran`s controversial nuclear programme, which resumed Saturday after a 15-month impasse, have been described as "positive" by a European Union official.
Known collectively as the P5+1, the six world powers -- US, Britain, France, China, Russia and Germany -- and Iran met in Istanbul, BBC reported.
The West accuses Iran of building nuclear weapons, but Iran maintains that its nuclear programme is for peaceful civilian purposes.
Michael Mann, a spokesman for EU foreign policy chief Catherine Ashton, said the talks were "totally different" from the last session 15 months ago.
"There is a positive atmosphere... contrasting with the last time," he was quoted as saying.
After a two-and-a-half-hour morning session, Mann said: "The principles for future talks seem to be there."
Russia earlier warned both sides not to "overblow the differences" between them.
"We really need to find a middle course," said Deputy Foreign Minister Sergei Ryabkov. "The negotiations are about renewing confidence."
US President Barack Obama earlier described this as the "last chance" for diplomacy to work, while Secretary of State Hillary Clinton said Iran had to "demonstrate clearly in the actions they propose that they have truly abandoned any nuclear weapons ambition".