OpenAI is reportedly in early talks about a sale of shares held by current and former employees that would value it at half a trillion dollars, overtaking Elon Musk's SpaceX. If the transaction goes ahead, the value of the ChatGPT developer would rise by about two-thirds, from 300bn ( 225bn). Musk's rocket companyis currently worth 350bn and is reportedly circling a 400bn price tag in a new fundraising. Bloomberg, which first reported the OpenAI talks, said existing investors, including Thrive Capital, have approached the company about buying employee shares. Other investors in OpenAI, which is based in San Francisco, include the Japanese investment company SoftBank, which led the 300bn financing, and Microsoft.

Currently, the biggest shareholders include media company Advance Magazine Publishers, Chinese tech firm Tencent, US investment firm Fidelity, and Sam Altman, the chief executive of ChatGPT makers OpenAI.

SoftBank Group said Tuesday that it will receive $5.12 billion in proceeds from the initial public offering of Arm Holdings, a British chip designer under the Japanese conglomerate, by the end of September. Arm, whose chips power most of the world's smartphones, debuted on the U.S. Nasdaq stock exchange last Thursday in the largest U.S. IPO this year, shooting its market capitalization to over $65 billion. The share sale is widely considered a success, given its first trading day's closing price of $63.59, some 25 percent above its IPO price of $51, reflecting investors' excitement over recent technological advances in artificial intelligence and Arm's increased role in supporting them. The proceeds will replenish the war chest of the Japanese investment giant, which posted massive losses in the past two years due to a fall in the value of tech start-ups it invests in amid unfavorable market conditions. Analysts said the share sale, together with the recent market recovery, could accelerate SoftBank's investment in AI-related venture firms as it has become easier for the Japanese company to raise funds using Arms shares as collateral.