AFP:World leaders Tuesday mourned the death of veteran US diplomat Richard Holbrooke, lauding the dogged negotiator as a colossus who against the odds brokered peace in conflict zones such as Bosnia. US President Barack Obama led the tributes to his special envoy to Afghanistan who died on Monday, calling him "a true giant of American foreign policy who has made America stronger, safer, and more respected". Balkan leaders praised Holbrooke for bringing stability to their region.