Iran, the United States and five other major powers are trying to reach an agreement to restrain the Iranian nuclear programme in exchange for relief from economic sanctions.
The following are answers to frequently asked questions about any nuclear deal and what follows, from analysts, economists and academics in Reuters Global Oil Forum:
Q: When will financial sanctions be lifted?
Richard Nephew, Program Director at the Center for Global Energy Policy at Columbia University
, in New York, said he thought international financial transactions with Iran involving U.S. entities would be possible sometime early in 2016:
"I would anticipate some would start in early 2016, but others will be more reluctant. It could take years for big banks that were burned to go back in."
Torbjorn Soltvedt, Middle East analyst at Verisk Maplecroft in Bath, England, said:
"There has been a lot of talk about a 'snapback' approach, where sanctions are lifted rapidly but are ready to be re-imposed on short notice. A gradual lifting still seems more likely, though. Probably banking sanctions will be lifted first, followed by insurance ... Frozen assets could be made available within weeks, though, as a first step."
"Most sanctions apart from those on the oil and gas sector could go quite soon."
Q: When will oil sanctions be lifted?
Scott Lucas, professor of International Politics at the University of Birmingham and founding editor of EA WorldView:
"U.S. sanctions are toughest to lift because of the web of both Executive Orders and Congressionally-mandated sanctions. Don't expect that to occur for months after deal is signed. The United States will wait until last possible moment for IAEA verification of Iranian compliance. Some sanctions may take up to a year to be fully removed, although it's important to realise that not all sanctions will take that long. It is a complex political, economic, and legal web because of the build-up of sanctions over decades."
"Oil sanctions would probably take longest (to lift) and could well stay in place until the middle of 2016.
"Oil and gas companies will need time to finalise negotiations in any case, so mid-2016 is not necessarily that bad. Improved fiscal terms are expected to be announced in September."
Q: How long before more Iranian oil gets to market?
A Reuters poll of 25 economists and oil analysts last week forecast 250,000 to 500,000 barrels per day (bpd) of extra Iranian crude oil could
come onto the world market by the end of this year. The poll expected an extra 500,000 to 750,000 bpd on the market by mid-2016.
"I think that is potentially too optimistic. I think that the oilfields may be in worse shape than we expect, that the Iranian system may be slow to get it going, that they'll have some difficulty in selling their overfilled storage, and that will make it hard to boost ... I think 500,000 bpd is in their reach."
"It will take a few months before Iran can start to export at full blast."
Edward Morse, global head of commodities research at Citi in New York:
"Sanctions have clearly impaired Iran's ability to maintain its mostly mature oilfields, let alone develop new projects."
Q: Once a deal is done, could sanctions be reimposed?
Possible, but very unlikely, analysts say.
"It would cost Iran too much - to the point of economic crisis - to break the agreement and get caught."
"There will be technical glitches. Iran will have to do a lot in a little amount of time. They are liable to get one or two things off-course. But I think that the big issues will be worked out, and that it will, in the end, be implemented."
(By Christopher Johnson; Editing by Kevin Liffey)