TOKYO, June 10 -- SoftBank Group Corp. was supposed to be proof that betting everything on artificial intelligence was a strategy, not a gamble. On Wednesday, the market decided to argue.

Shares of the Japanese technology conglomerate tumbled nearly 10% in Tokyo trading after Bloomberg reported that its talks with potential creditors to raise at least $6 billion from a margin loan backed by its OpenAI stake had stalled - just weeks after the company had already cut its initial $10 billion target by 40 percent. The reason lenders gave, according to people familiar with the matter who asked not to be identified, was the same one that makes the whole AI trade uncomfortable right now: no one could agree on what an unlisted startup's equity i...