BRUSSELS - Top negotiators from six world powers will meet in Brussels next week to discuss diplomatic efforts to defuse the Iran nuclear crisis, EU foreign policy chief Catherine Ashton’s office said Thursday. The meeting to be hosted by Ashton on Wednesday will be the first on the sensitive issue since the US election that saw President Obama returned to office and comes ahead of an expected new round of talks with Iran by early 2013 at the latest. Political directors from the so-called P5+1 group - the five permanent UNSC members, the US, China, Russia, UK and France, plus Germany - last met to discuss Iran’s N-programme in New York in September.