SoftBank Group has sold around a quarter of its stake in T-Mobile US for $4.8 billion, as the company seeks to fund its AI ambitions.

Reuters reported that the company sold 21.5 million T-Mobile shares at $224 each.

The shares were offered in a price range of $224 to $228 each, according to a term sheet that Reuters reviewed.

Despite the sale of the shares, SoftBank remains the second-largest shareholder in T-Mobile US, behind the carrier's parent company, Deutsche Telekom.

DT holds a 59 percent stake in the carrier.

Before SoftBank's stake sale, the Japanese company owned 85.36 million shares worth about $22.76 billion, according to LSEG data.

Early last year, SoftBank told T-Mobile to issue 48.75 million shares in common stock to it after conditions set out in an agreement made as part of the merger of SoftBank's US telco Sprint, and T-Mobile were met.

SoftBank has been splashing out on AI investments this year, and said in April it would put $30 billion into OpenAI. The company could withhold $10bn of its investment if the ChatGPT-maker doesn't restructure into a for-profit entity by December 31, a move that Elon Musk is trying to block in court.

Both OpenAI and SoftBank are backers of Stargate, a purported $500bn effort to build AI data centers for training and inference.

The pair are reportedly each expected to invest $19bn in Stargate - although OpenAI's investment will likely come from the funds raised in this round from SoftBank.