The past year has seen colossal investments in infrastructure needed to provide the computing power for artificial intelligence (AI), while share prices in the sector -- including SoftBank's -- have ballooned.

"SoftBank Group's mission is to realise Artificial Super Intelligence (ASI) for the advancement of humanity," SoftBank and DigitalBridge said in a statement late Monday announcing the deal.

"Achieving that vision requires breakthroughs not only in AI models, but also in the platform infrastructure needed to train, deploy, and serve them at global scale," the joint statement said.

Florida-based DigitalBridge manages around $108 billion worth of infrastructure assets including cellphone towers and data centres. The deal price includes debt.

Son, 68, a long-time ally of US President Donald Trump, made his name with spectacularly successful bets in firms like Chinese ecommerce titan Alibaba in the 1990s.

After suffering massive losses, Son is now seeking to pivot into AI and SoftBank recently raised $5.8 billion for new investments by selling its stake in US chip titan Nvidia.

SoftBank is a major investor in ChatGPT maker OpenAI, and with Oracle the two are leading the $500-billion Stargate project to build AI infrastructure announced by Trump in January.