Reuters reports that "Iran and major powers were struggling on Monday to reach a preliminary nuclear accord as 'gloom' set in, with both sides sticking to their positions a day before a self-imposed deadline."
"One sticking point concerns Iran's demand to continue with research into newer generations of advanced centrifuges. These can purify uranium faster and in greater quantities than those it currently operates for use in nuclear power plants or—if very highly enriched—in weapons. Another question involves the speed of removing the sanctions on Iran."
"Even if a framework deal is reached by the deadline, officials say it could still fall apart when the two sides attempt to agree on all the technical details for the comprehensive accord by the end of June."