If Iran and world powers couldn't clinch a nuclear deal after five hard months of bargaining, what hope is there that yet more time will help?

Quite a lot actually, experts told AFP.

Even though Iran and the five permanent members of the UN Security Council plus Germany remain far apart on key issues, some progress has been made, the analysts said.

"The chances are better than ever that there will be a final deal," said Richard Dalton, Britain's former ambassador in Tehran, now at the Chatham House think-tank.

"But hard work on the politics of it has to be done in Washington and Tehran," Dalton told AFP.

On Friday the parties announced an extension until November 24 of their July 20 deadline to reach a deal, prolonging and augmenting the terms of an interim accord struck last November.

This came after a 17-day, sixth and final round of negotiations in Vienna that saw US Secretary of State John Kerry jet in but fail to secure a breakthrough.

The mooted deal is aimed at dispelling fears that Iran might develop nuclear weapons, after a decade of rising tensions, Iranian nuclear expansion and bellicose rhetoric.

Iran, which denies wanting the bomb in the first place, in return wants the lifting of painful UN and Western sanctions strangling its economy.

- Two steps forward -

But the hoped-for agreement is both extremely ambitious and fiendishly complex.

Iran appears to have given ground on two things: the future of the Arak reactor, which could provide Iran with weapons-grade plutonium, and more stringent UN inspections.

Tehran has proposed changing the design of Arak so that much less plutonium can be extracted from the reactor's spent fuel rods.

More UN oversight of Iran's nuclear facilities would give the world added confidence that Iran is not secretly building a nuclear weapon.

But two problematic issues remain.

The first is how, and at what pace, to ease sanctions. Some are UN Security Council ones, others EU and still others US, making lifting them tricky.

The major sticking point however is uranium enrichment, a process which makes uranium suitable for peaceful purposes but also, when highly purified, for a nuclear weapon.

Iran wants to expand drastically its enrichment programme.

It says its needs to enrich for Bushehr, its only current nuclear power plant, once a deal with Moscow to supply fuel for Russian-built plant expires in 2021.

Iran also says it needs to make fuel for more nuclear power plants that it plans to build around the country.

But with years until the Russian contract expires, and any new facilities years if not decades away, the powers say Iran has no need for enrichment on a major scale.

They fear Iran's covert aim is to enrich uranium to weapons-grade, so the powers want cuts in Iran's capacities, and for a "double digit" number of years, a senior US official said this month.

- 'Innovative proposal' -

In an attempt to break the deadlock on this issue, Iran's Foreign Minister Mohammad Javad Zarif aired in the New York Times this week what he called an "innovative proposal".

It includes Iran agreeing to freeze its enrichment capacities at current levels, and for between three and seven years.

For Siavush Randjbar-Daemi, an Iranian lecturer at Manchester University, Zarif "cannot go back home and say he has agreed a freeze on all aspects related to enrichment."

While Zarif's proposal still remains unacceptable to the West, analysts said that it constitutes an opening gambit which could form the basis for serious negotiations.

Farideh Farhi, Iranian specialist at University of Hawaii, called the idea a "frame for what a final deal might look like."

Mark Fitzpatrick at the International Institute for Strategic Studies, said the proposals fell short of what is needed but that it was "noteworthy and positive that Iran is exploring various options".

"The key question is whether the supreme leader would allow the cut-backs to the enrichment programme that would be necessary for a deal," Fitzpatrick told AFP.

"He seems to have said that maintaining current capabilities is a redline. If so, I don't see how a final deal can be possible."