By Echo Wang and Joey RouletteNEW YORK, Jan 29 (Reuters) - Elon Musk's SpaceX and xAI are in discussions to merge ahead of a blockbuster public offering planned for later this year. Musk, the world's richest man, is the CEO of both the private space company SpaceX and the artificial intelligence company xAI, which controls his social media platform X. Musk, SpaceX, and xAI did not respond to requests for comment. Under the proposed merger, shares of xAI would be exchanged for shares in SpaceX. Last year, SpaceX agreed to invest $2 billion in xAI as part of the startup’s $5 billion equity ​fundraising, the Wall Street Journal reported at the time.