World powers and Iran on Wednesday wrapped up two days of talks in Kazakhstan aimed at breaking a decade of deadlock over the Iranian nuclear programme, but there was no sign they had achieved any breakthrough.

The first day of gruelling negotiations in an upscale hotel in the Kazakh city of Almaty had concluded Tuesday with both sides relieved to have pushed the talks along for another day.

The world powers of the United States, Russia, China, Britain, France and Germany had described the first day of the talks as "useful" without giving further details.

The second day began with a one-on-one session between EU foreign policy chief Catherine Ashton -- representing the world powers -- and chief Iranian negotiator Saeed Jalili.

All the nations involved then opened a full plenary session behind closed doors. The first day's session lasted three hours but on the second day it wrapped up in just one hour.

"Talks have concluded," said a Western official, adding that details of the meeting would be provided shortly. An Iranian official also confirmed that the talks had now concluded, without giving further details.

The powers made an offer to ease some sanctions on Iran in exchange for concessions on its disputed nuclear programme -- a proposal that had been discussed in various forms at three previous meetings in the past year.

Ashton's spokesman had made clear late Tuesday that it was very much up to Iran to respond to the offer, although Tehran had also said it was coming up with counter offers of its own.

"We hope very much that the Iranian side comes back (on Wednesday) showing flexibility and a willingness to negotiate," Ashton's spokesman Michael Mann said.

"The ball is very much in their court," Mann stressed.

On the table is an offer for the five permanent UN Security Council members and Germany to ease sanctions on Iran's gold and precious metals trade while simultaneously lifting some restrictions on the Islamic republic's banking operations.

The measures are meant to encourage goodwill in Tehran while encouraging it to stop enriching uranium to 20 percent -- a level seen as being within striking distance of military capabilities.

The powers also want Iran to shut the Fordo plant where such high-grade enriched uranium is produced and to ship out the existing stock it does not need for established medical purposes.

Iran counters that its rights to enrich uranium must be respected before negotiations can proceed any further.

Iran has also stipulated that it would only consider giving up enrichment to 20 percent if all forms of sanctions against it were lifted -- a condition unpalatable to Washington.

"We will not accept anything beyond our obligations and will not accept anything less than our rights," Iran's chief nuclear negotiator Saeed Jalili declared before setting off for Kazakhstan.

US Secretary of State John Kerry countered on a visit to Berlin on Tuesday that he hoped "Iran itself will make its choice to move down the path of a diplomatic solution".

Israel, the Middle East's sole if undeclared nuclear weapons power, has never ruled out attacking Iran's nuclear sites and the diplomacy is essentially aimed at avoiding such an outcome which would send shock waves across the region.

The Jewish state launched a unilateral attack against the Osirak nuclear reactor in Saddam Hussein's Iraq in 1981 and has spoken of Iran approaching the same "red line" that demanded immediate action.

Iran already has a nuclear power plant in the southern city of Bushehr -- built with Russian help -- but Iran's supreme leader Ayatollah Ali Khamenei has described atomic weapons as a "sin".