OpenAI CEO Sam Altman and other leaders in artificial intelligence testify in May before the Senate Commerce, Science, and Transportation Committee on Capitol Hill in Washington, D.C. OpenAI filed confidentially for an initial public offering Monday. Photo by Anna Rose Layden/UPI | License Photo

June 8 (UPI) -- Artificial intelligence company OpenAI confidentially filed for an initial public offering Monday, becoming the third in a well-known trio of U.S. AI companies to do so in the past few weeks.

Rival AI company Anthropic filed for an IPO on June 1, and SpaceX (which merged with xAI, also owned by Elon Musk) filed in late May. SpaceX's debut is set for Friday. All three are expected to be very lucrative for early investors, as they have valuations around $1 trillion, Axios reported.

OpenAI said in a post that there has been no decision on the IPO's timing yet.

"It may be a while because there are things we want to do that are likely easier as a private company," the post said.