World powers negotiating with a defiant Iran over its nuclear programme need to risk more and get more "creative" if they want to break a deadlock that threatens tipping into military conflict, analysts say.

After three high-level meetings in three months, the latest in Moscow last week, Iran and the P5+1 group (the United States, Britain, France, Germany, Russia and China), appear no closer to finding a way out of their almost decade-long confrontation.

Parallel efforts between Iran and the UN nuclear watchdog, the International Atomic Energy Agency, are in an even worse state, with no sign of a deal on enhanced cooperation that IAEA chief Yukiya Amano said was all but sealed when he visited Tehran a month ago.

The P5+1 want Iran to stop the most sensitive area of its nuclear work -- the enrichment of uranium to 20 percent purity -- as well as to shut its near bomb-proof underground facility in Fordo, and to ship out its existing stockpiles of higher-enriched fissile material.

Iran, which denies accusations it wants or has worked on developing nuclear weapons, is steadfastly refusing to comply without guarantees of sanctions relief and an unlikely P5+1 declaration that Tehran has a "right" to enrich uranium.

Neither side is expected to budge much in their positions.

EU foreign policy chief Catherine Ashton, the P5+1 chief negotiator, said after the last round of "tough" talks in Moscow that, although "critical issues" had begun to be tackled, "significant gaps" separated the two sides.

Iran and the world powers managed to keep the diplomatic track alive by agreeing to more discussions -- but at a lower level, between experts, to be held July 3 in Istanbul.

More senior-ranking discussions will only follow if those experts manage to drag the talks out of the impasse by finding some elusive bridging formula that escaped their superiors in Istanbul, Baghdad and Moscow.

"We are not going to find a way out of this stalemate without some creative thinking, and it is hard to do creative thinking in formal set-piece meetings," said Mark Fitzpatrick from the International Institute for Strategic Studies think-tank.

One way would be the opening up between the two key players, the United States and Iran, of an informal avenue of communication for "brainstorming," an approach that produced results with North Korea, former US state department official Fitzpatrick told AFP.

With Iran, this avenue might, for example, be used for finding mutually acceptable ways of easing sanctions, or a solution to one of the thorniest issues: that of Iran's demand that its "right" to enrich be accepted.

Multiple UN Security Council resolutions have called on Iran to suspend all enrichment, and Israel for one has made it clear that any watering down of this demand is a red line.

US President Barack Obama is also not about to make a promise that will lay him open to accusations from his Republican challenger in November elections, Mitt Romney, of being soft on Iran.

But hammering out some sort of statement acceptable to both sides, with substantial caveats, "is the kind of thing that needs to be explored informally," Fitzpatrick said.

Given that the P5+1 includes the very same five permanent members of the UN Security Council, a "more imaginative, less rigid handling" of its resolutions would be "helpful," said Rouzbeh Parsi from the EU Institute for Security Studies (ISS).

Moreover, an avenue of communication between Washington and Tehran might also encompass other issues of mutual interest -- Afghanistan, for example -- and progress here might create the goodwill needed to progress on the nuclear file.

Bilateral talks "would be very helpful because it could also enable the conversation to be enlarged," said Trita Parsi, National Iranian American Council president and author of the book on US-Iran diplomacy "A Single Role of the Dice."

How likely such a channel of communication is highly uncertain however, given mistrust built up between the two foes over more than three decades of enmity.

The US has made clear, albeit quietly, that it is ready for a bilateral meeting, but so far it has been spurned by Iran, whose regime hardliners would certainly slam such an encounter.

With the IAEA meanwhile, the watchdog's former deputy director general Pierre Goldschmidt proposed in May Iran be given a "grace period" in which to come clean about any past violations of the nuclear non-proliferation treaty (NPT) or undeclared facilities or material without fear of punishment.

Another avenue would be a more regional approach, drawing in other players in the Middle East.

That would have to include Israel, the area's sole if undeclared nuclear-armed state and not party to the NPT, due to be visited this week by Russian leader Vladimir Putin.

Any new approach is likely to be delayed, however, by the same factor that is also keeping the P5+1 negotiation process alive despite the lack of progress, namely the policy paralysis created by the US election.

Obama, who famously offered Iran an "extended hand" if it "unclenched its fist", is wary both of appearing weak on Iran by agreeing a half-baked deal, and of turning the crisis into a calamity by walking away from the talks.

But by treading water, the two sides are playing a dangerous game because, meanwhile, the West is piling ever more pressure on Iran with new sanctions -- the next ones will hit within the next week -- and allegedly with cyberattacks.

Iran meanwhile will likely "counter-escalate", believes Trita Parsi, by enriching uranium to 65 or even 95 percent, by ramping up output at Fordo and by stirring up tensions in the Gulf and the Strait of Hormuz.

"The six powers, but especially the Western group, have to overcome their anxiety about making a comprehensive bargain with Iran," Mark Hibbs, proliferation expert at the Carnegie Endowment for International Peace, told AFP.

"There's no silver bullet, but there has to be a certain amount of risk-taking ... There has to be creative diplomacy, there has to be flexibility, and both sides have to put something on the table that builds confidence that there is going to be a process."