Iran's supreme leader revealed Tuesday his country's demands for a massive long-term increase in its nuclear enrichment capability, laying bare huge gaps between Tehran and world powers negotiating a deal.

The comments, published on Ayatollah Ali Khamenei's website, represent a dramatic intervention in the talks currently taking place in Vienna between Iran and the P5+1 group of Britain, China, France, Russia and the United States, plus Germany, for a nuclear accord.

His remarks relate to the enrichment process of producing fuel from centrifuges for nuclear power stations, which the West and Israel says, in highly extended form, could be used to develop an atomic bomb.

Iran currently has about 19,000 centrifuges -- of which only 10,000 are working -- but says more powerful machines will be needed to develop enough nuclear energy in the future.

Khamenei said the required enrichment capability would be 19 times higher than the West currently wants to allow under a comprehensive agreement.

Uranium enrichment and centrifuge numbers are the most sensitive topic in the negotiations, which aim to conclude a deal by July 20.

But with less than two weeks until that deadline, the supreme leader's remarks exposed a gulf that still exists between Iran and the leading nations, who are seeking to curb Iran's nuclear activities.

Referring to the machine used in uranium enrichment, Khamenei, who has the final word on all matters of state, said: "Their aim is that we accept a capacity of 10,000 separative work units, which is equivalent to 10,000 centrifuges of the older type that we already have.

"Our officials say we need 190,000 (SWU). Perhaps not today, but in two to five years that is the country's absolute need."

- Differences with Russia -

An Iranian diplomat, quoted anonymously by the official IRNA news agency, said foreign ministers from the P5+1 countries would travel to Vienna this week, probably on Friday, to help clinch an accord.

But France's foreign minister, Laurent Fabius, on Tuesday indicated divergences have emerged between Russia and the Western powers involved in the negotiations to secure an agreement, without specifying what they were.

"Whereas until now the P5+1 had a very homogeneous attitude, in the past days representatives in the negotiations have put forward a certain number of different approaches between part of the 5+1 and our Russian partners," he said.

Fabius said that, while negotiations on the accord had begun, "none of the main issues" have so far been resolved.

Any nuclear deal would involve a framework and years of monitoring, but Khamenei's open declarations throw into doubt the room for compromise.

According to American media reports, the United States may accept Iran having 2,000-4,000 low-powered, first generation centrifuges.

France's Fabius said last month Iran could retain "several hundred centrifuges" but he disclosed that the Iranians were asking for "hundreds of thousands".

The accord being sought by the P5+1 aims to finally end talk of possible US or Israeli military action against Iran. The Islamic republic has always denied seeking an atomic bomb.

In exchange for an agreement, Iran wants punishing Western sanctions to be lifted.

Deputy Foreign Minister Abbas Araqchi, a leader of Iran's negotiating team, welcomed the supreme leader's comments and tweeted that he and his colleagues "would not give up any of our nuclear rights."

With Sunni Arab insurgents overrunning large parts of Iraq, and Syria in chaos from civil war, a nuclear deal could help Tehran and the West normalise ties at a particularly explosive time.

- 'Unique opportunity' -

Iranian Foreign Minister Mohammad Javad Zarif has described the talks as a "unique opportunity to make history", saying success would allow both sides to address "common challenges" like Iraq.

The talks have been aiming to secure an agreement by July 20, when an interim deal struck in November expires.

The six powers want Iran to drastically reduce its nuclear activities to render any drive for a weapons capability all but impossible.

The deadline could potentially be extended by up to six months, and many analysts believe this is already being negotiated.

But US President Barack Obama, facing midterm elections in November, is wary of doing anything that could be construed by his Republican opponents as giving Iran more time to get closer to having the bomb.

This is the longstanding accusation of Israel, the Middle East's sole if undeclared nuclear-armed state.