The powers insist that the most severe penalties, which are on oil exports and banks, will remain until there is a comprehensive agreement to minimize Iran's nuclear arms-making capacity. Iran says it does not want such weapons and has indicated it's ready to start rolling back its program but wants greater and faster sanctions relief than that being offered.
Experts believe countries like China, Korea and India which have been given exemptions to U.S.-led sanctions and allowed limited imports of Iranian crude may look to increase their purchases from the Islamic Republic if negotiations fail to reach a deal soon.
Brent crude, the benchmark for an international variety of crude, was up 71 cents to $110.79 a barrel on the ICE futures exchange in London.
In other energy futures trading on Nymex:
Wholesale gasoline rose 0.41 cent to $2.7232 gallon.
Heating oil added 2.07 cents to $3.0263 a gallon.
Natural gas advanced 4.5 cents to $3.747 per 1,000 cubic feet.