U.S. stocks fell Wednesday ahead of a quarterly report from Nvidia, Wall Street's centerpiece event of the week that could shatter or add fresh fuel to a rally driven by optimism around artificial intelligence.

Shares of the dominant seller of AI processors, due to report after the closing bell, dipped, trimming their gain so far this year to around 150%.

Following several blowout quarterly reports, Nvidia is viewed as the biggest winner so far from AI technology. Its latest results follow concerns about increases in already-hefty spending by Microsoft, Alphabet and other major players in the race to dominate emerging AI technology.

"It's been the poster child for the AI boom and it's really led the charge, so it would be hard for the market to move on in spite of a disappointment from Nvidia," warned Keith Buchanan, senior portfolio manager at GLOBALT Investments in Atlanta.

"Nobody has their arms around how long Nvidia can continue to surprise on the upside, but, naturally, it can't last forever," Buchanan added.

Options pricing shows traders anticipate a move of around 9.8% in Nvidia's shares on Thursday, a day after it reports its results, data from analytics firm ORATS showed.

Other chip stocks also dipped, with Broadcom and Advanced Micro Devices each losing ground.

Google-owner Alphabet, Microsoft and Amazon also fell.

According to preliminary data, the S&P 500 lost 33.30 points, or 0.59%, to end at 5,592.50 points, while the Nasdaq Composite lost 198.79 points, or 1.12%, to 17,556.31. The Dow Jones Industrial Average fell 156.26 points, or 0.38%, to 41,094.24.

Investors widely expect the U.S. Federal Reserve will lower interest rates at its September meeting after Fed Chair Jerome Powell's support for imminent policy adjustment last week sparked broad-based market gains.

The CME Group's FedWatch Tool currently sees a 64% chance of a 25-basis point reduction and a 37% chance of a 50-bps cut.

The Personal Consumption Expenditure report for July, due on Friday, may provide further insight into the central bank's likely rate-cut trajectory.

Super Micro Computer tumbled after the AI server maker said it would delay the filing of its annual report for the fiscal year ended June 30, a day after Hindenburg Research disclosed a short position in the company.

The market value of billionaire Warren Buffett's Berkshire Hathaway briefly surpassed $1 trillion for the first time.