A second day of nuclear talks between Iran and world powers has been under way in Geneva amid cautious statements by the top negotiators.
The talks, which began on November 20, are focusing on efforts to agree upon a six-month suspension of Iran's nuclear activities in exchange for limited relief for Tehran from Western sanctions.
Michael Mann, a spokesman for the powers' chief negotiator, indicated that Catherine Ashton and Iranian Foreign Minister Mohammad Javad Zarif held a substantive opening meeting on November 21, which would continue in the afternoon.
"It was not your classic bilateral [meeting], " he said. "It was a real meaningful, detailed, substantial negotiation trying to drill down into the details of the text to try and narrow the differences that still existed after the last round.
"[EU foreign policy chief Catherine Ashton and Iranian Foreign Minister Mohammad Javad Zarif] spoke for about two and a half hours this morning, they've broken, briefly, and they're going to come back to the talks again...to continue for as long as it takes. This is a serious negotiation and Catherine Ashton is determined to try and progress things as fast as she can but also make sure that it is a watertight and solid deal."
Zarif told Iranian television that the meeting was held in "a positive atmosphere," but noted disagreements "on important issues."
Zarif's deputy, Abbas Araqchi, told reporters in Geneva that consistent disagreements remain between the two sides.
"I'm not in a position to go into the details of [the negotiations] but we have some major differences still and those details are almost on every side," he said.
On November 20, the P5+1 group of world powers consisting of the United States, Russia, China, Britain, France, and Germany opened a new round of discussions in Geneva after an inconclusive first round held in the same city earlier this month.
However, the first round brought the two sides closer than ever before, generating momentum and guarded optimism that an agreement would be possible.
Iran claims the right to enrich uranium as a signatory to international nuclear treaties and says its program is entirely peaceful. Western powers suspect Iran of seeking nuclear weapons capabilities under the cover of its nuclear program.
The six powers want Iran to stop enriching uranium to 20 percent, a short technical step from weapons-grade levels. They a are also concerned over a research reactor under construction at Arak in western Iran which will produce weapons-grade plutonium.
The current effort to reach a six-month suspension of Iran's nuclear activities in exchange for sanctions relief is intended as a confidence-building measure.
Negotiators hope such an agreement might then provide momentum for a later comprehensive settlement of the Iran nuclear crisis.
With reporting by AFP and Reuters