Iran and six world powers are meeting for a second day in attempts to find common ground over concerns that Tehran's nuclear program might be used to make weapons.
Chances of progress at Saturday's session are unclear, however, after a first round ended with the two sides unable to reduce substantial differences.
The six insist Iran cut back on its highest grade uranium enrichment production and stockpile, fearing Tehran will divert it from making nuclear fuel to form the material used in the core of nuclear warhead.
Iran insists it has a right to enrich but says it has no interest to use the technology to make weapons. It wants more sanctions relief than the six are offering for any concessions on its part.