Agreeing a venue for the next round of talks between Iran and six world powers on Tehran's nuclear drive was hard enough. Achieving progress will be tougher still, analysts say.

Following weeks of wrangling, Iran and the P5+1 -- the US, China, Russia, Britain, France and Germany -- finally confirmed on Tuesday that they would meet in Almaty, Kazakhstan on February 26.

It will be the first such meeting since last June in Moscow, and the first since US President Barack Obama's re-election in November, a victory seen by many as freeing Washington's hands to strike a deal.

Watching closely will be Israel, the Middle East's sole if undeclared nuclear-armed state, which has warned it could bomb Iran, although the immediate threat appears to have receded in recent months, experts say.

"The Iranian danger has grown," President Shimon Peres said Tuesday. "It threatens our existence, the independence of the Arab states, the peace of the whole world."

Iran insists its nuclear programme is peaceful but many in the international community suspect that Tehran's real aim is to develop the atomic bomb.

The UN Security Council has imposed four sets of sanctions on Tehran, and further unilateral sanctions by the United States, the European Union and others began to cause Iran major economic problems in 2012.

"The sanctions are biting," Siavush Randjbar-Daemi, a Middle East and Iran lecturer at Manchester University in England, told AFP. "The currency has plunged badly and... the price of absolutely everything has skyrocketed."

In May in Baghdad, the P5+1 demanded Iran scale back uranium enrichment to purities of 20 percent, which for the international community is the most worrisome part of Tehran's activities.

But because the P5+1 stopped short of offering relief from the sanctions, Iran walked away at the next round of talks in Russia. The lengthy US election campaign then put all further efforts on hold.

-- 'Updated' offer --

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British Foreign Secretary William Hague said Tuesday that the world powers would make an "updated and credible" offer and that the "need to make progress is increasingly urgent".

Russia's chief negotiator, Deputy Foreign Minister Sergei Ryabkov, was quoted Wednesday by RIA Novosti as saying he hoped to see at the talks "if not an outright breakthrough -- then serious progress".

"The key question is whether Iran will come in a real transactional mode, in other words really be ready to negotiate. They haven't been so far," said Mark Fitzpatrick, a former US State Department official now at the International Institute for Strategic Studies.

"I think the P5+1 are ready to haggle and negotiate. So far I haven't seen signs that Iran is," he told AFP.

The run-up to Tuesday's announcement of new talks did not bode well, with P5+1 chief negotiator Catherine Ashton's office complaining that Iran had "come back to us again and again with new pre-conditions".

Comments from Mahdi Mohammadi, a member of Iran's negotiating team, indicated recently that the positions of the two sides remain poles apart.

First, the United States had to accept Iran's "right to enrich", then the US and EU have to remove all unilateral sanctions, Mohammadi said.

Only then, he said, would Iran be "ready to negotiate about 20-percent enrichment provided that the United Nations Security Council will annul all its sanctions resolutions against Tehran".

Iranian Foreign Minister Ali Akbar Salehi appeared to strike a more conciliatory note in an interview in Germany's Handelsblatt published Wednesday, saying Tehran "takes the concerns of the other side seriously".

"But at the same time our right to civilian uses of nuclear power... must be recognised," he said, while calling for an end to "war rhetoric that all options are on the table and threats of more sanctions."

For Mark Hibbs at the Carnegie Endowment for International Peace, success in Almaty and beyond is about building trust and "sequencing" -- the order in which both sides agree to take steps.

"If you lift sanctions too early in the process and your negotiations fall apart, it may be very very difficult for you to impose those sanctions after they have lifted them," Hibbs told AFP.

"And that is particularly the case for the unilateral (EU and US) sanctions."

And it is not just Iran and the P5+1 that have to agree on the right order, the six powers also have to speak as one -- something which going forward is not necessarily a given, Hibbs said.

"There could be differences of opinion," he said.