VIENNA: The major powers are trying to resolve the difficult issue of when to remove a UN arms embargo, a senior Western official said on Thursday after Russian Foreign Minister Sergei Lavrov said it should be lifted as soon as possible. 'This is not a new position for Russia. That said, we are working collectively on a way forward on this difficult issue,' the senior Western official said. Iran and six major powers - Britain, China, France, Germany, Russia and the United States - are negotiating a deal under which Iran would curb its nuclear programme in exchange for relief from economic sanctions.