SoftBank Group is aiming to increase its stake in OpenAI by acquiring up to $1.5 billion in shares from the startup¡¯s employees, according to people familiar with the matter.

The company will make a tender offer for the stock, allowing OpenAI employees to cash in shares if they choose. SoftBank contributed $500 million to OpenAI¡¯s $6.6 billion fundraising round in October, but had pushed for a larger allocation at the time, said one of the people, asking not to be named because the negotiations aren¡¯t public.

SoftBank founder Masayoshi Son has vowed to step up investments in artificial intelligence as his Tokyo-based company regains its financial footing after years of missteps. OpenAI, which jumped out to early leadership in the field with its ChatGPT product, was valued at $157 billion in the last fundraising.

It¡¯s not yet clear how much stock SoftBank will be able to buy from OpenAI¡¯s employees, who may choose to hold onto their shares if they forecast bright prospects ahead.

SoftBank and OpenAI didn¡¯t respond to requests for comment outside of normal business hours.

The SoftBank tender offer is set to close this week, according to CNBC, which first reported the news.