At a long-awaited meeting Saturday in Istanbul, representatives from Iran and six members of the U.N. Security Council agreed to hold another round of negotiations over Iran's controversial nuclear program. Saturday's talks came after a year without negotiations, in which threats of military attack by Israel have escalated and Western nations have imposed crippling economic sanctions. European foreign-policy chief Catherine Ashton praised the opening discussions, calling them "useful and constructive." A Western diplomat said Iran had shown "serious engagement" and been willing to discuss "the heart of the issue." The next talks will take place in Baghdad on May 23 and could lead to Tehran allowing inspectors at all nuclear sites, despite having refused to do so in January.