Elon Musk has unveiled his latest big-money project: saving humanity from destruction by artificial intelligence.

The man who made his billions from PayPal and who has gambled a chunk of his fortune on the race for space, has warned frequently that AI represents humanity's greatest existential threat.

He is joining forces with other tech entrepreneurs to establish a $1 billion investment fund for researchers to pursue applications with a positive social impact and to try to stay one step ahead of the technology.

"Because of AI's surprising history, it's hard to predict when human-level AI might come within reach," they said in a statement. "When it does, it'll be important to have a leading research institution which can prioritise a good outcome for all over its own self-interest."