Iran's ambassador to the International Atomic Energy Agency (IAEA) Reza Najafi attends a news conference at the headquarters of the IAEA in Vienna December 11, 2013. REUTERS/Leonhard Foeger
VIENNA (Reuters) - Experts from Iran and six world powers laboured for a fourth day on Thursday to work out exactly how to implement last month's breakthrough deal for Tehran to curb its nuclear programme in return for limited sanctions easing.
The length of the closed-door discussions at the Vienna headquarters of the U.N. nuclear watchdog indicated the complexity of the task, not necessarily any major disagreements.
