Iran, the United States and the European Union began an unscheduled second day of talks in Oman on Monday on disagreements hindering resolution of a confrontation over Tehran's nuclear program, U.S. and Iranian officials said.

With two weeks to a deadline for an overall agreement, Iranian Foreign Minister Mohammad Javad Zarif, U.S. Secretary of State John Kerry and EU envoy Catherine Ashton met in Oman's capital Muscat to tackle a decade-long dispute that has raised the risk of wider conflict in the Middle East.