* Bitcoin briefly falls below $90,000 mark * Ether falls more than 4% * Worries over AI gains hit risk sentiment By Gregor Stuart Hunter SINGAPORE, Dec 11 (Reuters) – Cryptocurrencies tumbled on Thursday and bitcoin fell back below the $90,000 threshold in a renewed signal of market unease over market concerns. shares. Risk sentiment soured after U.S. cloud firm Oracle’s profit and revenue outlook missed forecasts and executives flagged higher spending — a sign that AI infrastructure spending is not turning a profit as quickly as investors had hoped. Bitcoin was last down 2.5% at $90,056.24, while ether tumbled 4.3% to $3,196.62, erasing the gains of the past two days, extending weakness that started in the US trading session on Wednesday after the Federal Reserve cut interest rates. Shares in Asia fell and futures pointed to lower opens in Europe and the United States. “What we saw last night was even though risk assets did well, crypto didn’t really want to know about it,” said Tony Sycamore, market analyst at IG in Sydney. “The crypto space really needs to see more convincing evidence that the washout that we saw from that October 10 sell-off is complete, and at this point in time, it just doesn’t look like it’s there.” Standard Chartered on Tuesday reduced its expectations for bitcoin to reach $200,000 by the end of 2025, lowering its forecast to $100,000. “We think the purchase by Bitcoin digital assets treasury companies is probably over,” said Geoff Kendrick, global head of digital assets research at Standard Chartered. “As a result, we now think future Bitcoin price increases will effectively be driven by only one leg – ETF purchases.” (Reporting by Gregor Stuart Hunter; Editing by Jamie Freed)