pbr A healthy-looking Fidel Castro has appealed to President Barack Obama to prevent a global nuclear war.br ppbr His speech to parliament marked his first official government appearance since emergency surgery four years ago.br ppbr Castro, who turns 84 in a week, arrived on the arm of a minder, waving and smiling as the crowd applauded loudly in unison.br ppbr Dressed in olive-green fatigues without military insignias, he immediately took the podium and delivered a fiery 11-minute speech on his fears of an impending global nuclear war.br ppbr Asked by one parliamentarian if US President Barack Obama would be capable of starting a nuclear war, Castro replied, "No, not if we persuade him not to."br ppbr Castro's participation in Saturday's legislative session marks the revolutionary's first official government act and his first joint appearance with Raul Castro since emergency intestinal surgery in 2006.