Iran Nuclear Talks Get Down to Nitty-Gritty, Britain 'Not Optimistic'

British Foreign Secretary Philip Hammond expressed doubt Wednesday that a landmark nuclear deal between Iran and six world powers would be reached by the deadline next week and spoke of the possibility of an extension.

"I am not optimistic that we can get everything done by Monday, but I think if we make some significant movement, we may be able to find a way of extending the deadline to allow us to get to the final deal, if we are making good progress in the right direction," he told reporters in Latvian capital Riga.

"There will need to be some considerable further flexibility shown by the Iranian negotiators over the next four or five days if we are going to get to that deal," said Hammond, whose country is one of the six world powers involved in the talks.

He spoke after meeting with his Latvian counterpart Edgars Rinkevics as the deadline loomed to reach the accord, which is aimed at easing fears that Tehran might develop nuclear weapons under the guise of its civilian activities -- an ambition Iran denies.

The accord between Iran and the P5+1 -- the U.S., China, Russia, Britain, France and Germany -- could resolve a 12-year standoff, silence talk of war and help normalize Iran's relations with the West.

"The prize is very big: a resetting of relationships between Iran and the West if we can do this deal," Hammond said.

"We do very much want to see a deal done in Iran but we don't want to do a bad deal. Better no deal than a bad deal.

"The right deal with Iran has to be one which gives us the assurance we need that Iran's program is exclusively targeted at civil nuclear use, has no military dimension at all and where Iran's enrichment capacity is limited to a level that doesn't present any military threat," he concluded.

Earlier on Wednesday, Iran and six world powers got down to business in Vienna, groping for the elusive magic formula to secure a milestone nuclear deal that satisfies hardliners in Tehran and Washington.

The clock was ticking ever louder however on the second day of this final round of talks, with just five more days for Iran and the five permanent members of the U.N. Security Council plus Germany to get a deal.

Foreign ministers were expected in the Austrian capital later in the week, but the U.S. State Department made clear that Secretary of State John Kerry, currently in London, would not arrive until Thursday afternoon at the earliest.

Kerry remained in London Wednesday before talks in Paris Thursday with the foreign ministers of France, widely seen as one of the toughest on Iran of the six powers, and of Saudi Arabia -- itself no friend of Iran.

Russian Foreign Minister Sergei Lavrov, whose country is a crucial player in the talks, will only come to Vienna if there is sufficient progress, Moscow's lead negotiator Sergei Ryabkov told Russian media late Tuesday.

"Right now a lot depends on Kerry's visit. Reaching a deal depends on the willingness and ability of the United States to lift sanctions" on Iran, Russian agency RIA Novosti quoted a Russian source as saying.

Upping the ante ahead of the deadline, Iran's Foreign Minister Mohammad Javad Zarif, said a deal was "possible" but only if the six powers did not ask for too much.

"If, because of excessive demands... we don't get a result, then the world will understand that the Islamic Republic sought a solution, a compromise and a constructive agreement and that it will not renounce its rights and the greatness of the nation," Zarif told Iranian media.

But Kerry, who held the latest in a string of meetings with Zarif in Oman last week, put the onus on Iran.

"It is imperative that Iran works with us with all possible effort to prove to the world that the program is peaceful," Kerry said.

British Foreign Secretary Philip Hammond echoed his comments, calling for more "flexibility by the Iranians to convince us that their intentions in their nuclear program are entirely peaceful".

The landmark accord being sought by Monday's deadline, after months of negotiations, is aimed at easing fears that Tehran might develop nuclear weapons under the guise of its civilian activities.

It could resolve a 12-year standoff, silence talk of war, help normalize Iran's relations with the West, boost the beleaguered Iranian economy and mark a rare foreign success for U.S. President Barack Obama.

In order to make it virtually impossible for Iran to assemble a nuclear weapon, the U.S., China, Russia, Britain, France and Germany (the P5+1) want Iran to scale down its nuclear program.

Iran, which insists its nuclear aims are exclusively peaceful despite failing to declare parts of its program in the past, wants painful sanctions lifted.

Some areas appear provisionally settled. But the big problem is enrichment -- rendering uranium suitable for power generation and other peaceful uses, but also, at high purities, for a weapon.

Iran wants to massively ramp up the number of enrichment centrifuges -- in order, it says, to make fuel for a fleet of future reactors.

The West insists on slashing the number, saying Iran has no such need in the foreseeable future. Russia is contracted until 2021 to fuel Iran's only power reactor and last week signed a deal to build -- and fuel -- several others.

The other major point of contention is the pace at which the tangle of sanctions -- U.N., U.S., EU -- is lifted, an area where Iranian expectations are "excessive", one Western diplomat said.

Given the differences, many analysts expect more time to be put on the clock, perhaps by agreeing certain areas and leaving others for further discussion.

The alternative -- walking away -- would be "catastrophic" and "foolish", Arms Control Association analyst Kelsey Davenport told AFP.

For now though, with another extension presenting risks of its own -- fresh U.S. sanctions, not least -- officials insist that they remain focused on getting the job done in time.