The U.N. nuclear watchdog (IAEA) had talks with Iran on Tuesday to advance a long-stalled investigation into Tehran's atomic activities, but it was not immediately clear whether any headway was made, leaving open the possibility agreements might be made later. They were expected to discuss IAEA requests for information about detonators that can be used to set off a nuclear explosive device. How Iran responds is regarded as a litmus test of its readiness to allow investigation into the possible military dimensions of the country's nuclear program. The IAEA-Iran talks were separate from those about to resume between the US, UK, France, China, Russia plus Germany (P5+1) in Vienna to draw up a draft agreement providing comprehensive solutions to the Iranian nuclear issue. These talks will need to overcome differences on Iran's uranium enrichment capacity, the heavy-water reactor at Arak and the possible military dimensions of Iran's nuclear programme. See also http://www.iranwatch.org/weapon-programs/nuclear