Kerry hunkering down for Iran nuclear talks

US Secretary of State John Kerry was to meet again Monday with his Iranian counterpart seeking to narrow serious gaps blocking a historic nuclear deal with a deadline just days away, AFP reports.

One of Kerry's goals in prolonging an overseas trip to visit Vienna was "to have in-depth discussions" with Iranian Foreign Minister Mohammad Javad Zarif and "to gauge Iran's willingness to make the critical choices it needs to make," a senior State Department official said.

"That's a pretty serious and potentially lengthy conversation."

With just six days until Sunday's July 20 deadline to strike a deal, the differences appear considerable.

Kerry and other Western ministers failed at the weekend to reach a breakthrough as they seek a treaty which would finally dispel all fears that Iran might develop nuclear weapons under the guise of its civilian programme.

Iran denies seeking the atomic bomb and wants the lifting of all UN and Western sanctions, which have crippled its economy.

Without making any predictions, the State Department official said Kerry would "take the time necessary... to see if progress can be made."

The five permanent members of the UN Security Council plus Germany have been negotiating almost non-stop for months, after sealing an interim accord in November under which Iran froze its uranium enrichment in return for about $7 billion in sanctions relief.

But the talks to nail down a full treaty have met major sticking points, particularly on how much of Iran's nuclear programme to dismantle.

Both sides are also under intense domestic pressure.

Beyond the negotiating table in Vienna, Zarif will have to come up with a deal that satisfies Iran's hardline Islamic leaders, while Kerry is under pressure from Congress ahead of November mid-term elections not to concede too much to Washington's traditional foe.

The United States and Iran have not held diplomatic ties for three decades, making the face-to-face talks between the two top diplomats all the more remarkable.

Zarif appeared to be in for the long haul too, telling Iranian media late Sunday there were still "seven difficult and tough days for discussion."

Iran needs to make concessions

But Germany's Foreign Minister Frank-Walter Steinmeier, who like his other counterparts from Britain and France held one-on-one talks with Zarif on Sunday in Vienna, was the most pessimistic warning that "the ball is in Iran's court".

"It is now up to Iran to decide to take the path of cooperation... I hope that the days left will be enough to create some reflection in Tehran," he said.

Britain's Foreign Secretary William Hague said there had been no "decisive breakthrough" and a "huge gap" remained on the key issue of uranium enrichment.

This activity can produce fuel for the country's sole nuclear plant or, if further enriched, the matter for an atomic bomb.

The six powers want Iran to reduce dramatically the scope of its enrichment programme, while Tehran wants to expand it.

Israel, the Middle East's sole if undeclared nuclear weapons state and which together with Washington has refused to rule out military action, is opposed to any enrichment by Iran.

Israeli Prime Minister Benjamin Netanyahu warned Sunday that any nuclear deal leaving Iran with the capability to pursue this activity would be "catastrophic".

"It would be a disaster for the United States and for everyone else," he told Fox News.

Iranian negotiator Abbas Araqchi was Sunday publicly sticking by Iran's position on enrichment which he called "clear and rational."

"As the supreme guide said, the enrichment programme has been planned with the real needs of the country in mind, meaning our need to ensure reactor fuel."

If no agreement is reached by Sunday when the six-month interim accord runs out, all sides can agree to extend the talks for a further six months.