A tepid push higher by U.S. stocks ran out of steam ahead of midday, with the Dow Jones Industrial Average dropping by more than 300 points and the S&P 500 dipping below an important, near-term chart support at its 50-day moving average.

Stock futures are falling in early trading Wednesday with the economy and tumbling AI stock prices serving up a twin threat to markets. The three main indexes had their worst day in more than a month on Tuesday, dragged down by weak ISM manufacturing data, which reignited fears that the U.S. economy is slowing.

The Dow Jones dropped Wednesday ahead of jobs data and the Fed's Beige Book. Nvidia stock extended Tuesday's dive.