Saudi Arabia has scaled back lofty ambitions for its NEOM gigaproject to prioritize completing elements essential to hosting global sporting events over the next decade as rising costs weigh, three sources told Reuters a day after the sudden departure of the project's longtime CEO.

The authoritarian country is spending billions on international athletics, from Formula 1 to combat sports, to boost its bottom line and image.

The change in leadership comes at a pivotal time for the $1.5 trillion green, megacity project central to the ambitious agenda of Saudi Vision 2030.

Nasr, the long-time chief executive of the $500 billion NEOM mega-project at the heart of Saudi Arabia's drive to diversify away from oil, has departed, NEOM said on Tuesday without giving a reason.

Saudi Arabia's ambitious futuristic city plans have been bogged down by delays and changes. The most recent is the departure of its CEO, Nadhmi al-Nasr.