BERLIN, Feb 12 (Reuters) - NATO Secretary-General Jens Stoltenberg will end his term as planned in October, a spokesperson for the alliance said, after a newspaper reported a further extension was in the works. "The mandate of Secretary-General Jens Stoltenberg has been extended three times, and he has served for a total of almost nine years," NATO spokesperson Oana Lungescu said late on Saturday. See here for a complete list of exchanges and delays