RIYADH/DUBAI, April 22 (Reuters) - Saudi Arabia is poised to officially appoint Aiman al-Mudaifer as the chief executive of NEOM, the $500 billion mega-project at the heart of the kingdom's drive to diversify away from oil, two sources familiar with the matter said on Tuesday.

Mudaifer has been NEOM's acting CEO since November, succeeding Nadhmi al-Nasr, the long-time former chief of the ambitious Red Sea urban and industrial development project that is nearly the size of Belgium.

Saudi Arabia's wealth fund PIF was not immediately available for comment.

(Reporting by Pesha Magid in Riyadh and Federico Maccioni in Dubai, Writing by Nayera Abdallah, Editing by Louise Heavens)

((Nayera.Abdallah@thomsonreuters.com;))