Nuclear negotiators are at odds over unknown nuclear facilities in Iran. Photo: Nanking2012 via Wikimedia Commons.

Over the past 20 months, world powers seeking a nuclear deal with Iran have worked out tentative agreements to monitor and secure the country’s known nuclear facilities to prevent it from building a bomb.

But as negotiations head for a June 30 deadline, diplomats are still at odds over a tougher issue: how to keep tabs on military bases and other sites where the Iranians might secretly work on a weapon.

Read full story at Stars and Stripes.