Iran and world powers have concluded a surprisingly cordial summit in Kazakhstan that appears to have given a gentle nudge to the decade-long nuclear stalemate, experts say.

Two days of talks in the soaring Tien Shan mountain city of Almaty concluded on Wednesday amid continued sabre-rattling from Israel and worry on international oil markets about the prospects of yet another Middle East war.

But Iran and the five permanent members of the UN Security Council -- the United States, China, Russia, Britain and France -- plus Germany, did agree to hold new talks on the Islamic republic's disputed nuclear drive in the coming weeks.

Iran flatly denies charges that it is enriching uranium at an increasingly rapid pace in order to one day build a nuclear weapon.

But Israel and its main ally the US have few doubts this is exactly the case.

The issue has been debated on three prior occasions in the past year alone. The last meeting between Iran and the leading powers, known as P5+1, ended in June without the sides able to agree to meet again.

Things went differently this time. The meeting saw the leading powers offer Iran a softening of non-oil or financial sector-related sanctions in exchange for concessions over its uranium enrichment operations.

Encouraged by the possible sanctions relief, Tehran said the parties had agreed to hold their next meeting at the same venue on April 5-6, after talks between senior civil servants on the issue in Istanbul next month.

"Some of the points raised in their (the world powers') response were more realistic, compared to what they said in the past," chief Iranian negotiator Saeed Jalili told reporters in words that amounted to rare praise.

Iranian President Mahmoud Ahmadinejad later added that "negotiations are better than confrontation", while Foreign Minister Ali Akbar Salehi said "things are taking a turning point".

The tone -- if not the actual content of what was achieved in Kazakhstan -- left some analysts both surprised and impressed.

"This is interesting because what we are seeing is the start of a process," said Moscow's PIR nuclear safety research institute analyst Andrei Baklitsky.

"The positions are slowly starting to merge. In other words, there are finally things there for them to discuss."

One analyst said the key was to break the initial ice and find a single issue around which future contacts could build.

"The most important development is that we might have a basis for further negotiation. In all previous talks, each side categorically dismissed the other's opening position," said Shashank Joshi of the Royal United Services Institute.

All sides agree there is little more time to waste and it is unclear what impact there will be from a looming June 2013 presidential vote in which Iranians will elect a successor to Ahmadinejad.

The sanctions are starting to bite at home and Jalili may be prepared to offer more flexibility if ordinary Iranians are starting to tire of their increasing isolation from the global economy.

US officials have been keen to call the Almaty session "useful" -- a more neutral word than either "positive" or "negative."

But they also pointed out that a good atmosphere during negotiations does not necessarily produce workable compromises.

"What matters are the results," a senior US official said.

"You care about the atmospherics, but in the end, you need concrete results," said the official.

And those -- in Washington's eyes -- would see Iran halt uranium enrichment to the 20-percent levels experts view as within striking distance of weapons-grade matter.

Iranians like Jalili argue that the West is not even making 20-percent enrichment an issue worthy of discussion at this stage -- a claim refuted by the US official.

Yet there is little doubt that the spirit of the discussion has changed.

"In past meetings, the approach centred on coercion: the main motivator for concessions was the threat of new sanctions and other escalatory steps," said National Iranian American Council President Trita Parsi.

"That approach has failed as Iran responded with its own escalation: it expanded its enrichment activities, installed new and improved centrifuges and amassed more enriched uranium."

That policy ran the region toward the very real danger of Israeli action -- a convincing argument for a strategy shift.

Now the world powers appear to be willing to take the first step by offering sanctions relief, and may find a more responsive Iran in return, experts say.

"Jalili's positive, conciliatory statements today represent a meaningful shift away from that pattern of mutual disdain," said Joshi.

"It makes it more likely that Iran will, in due course, be able to come up with a more realistic counter-offer."