S&P 500 has its worst day since mid-June as interest rate concerns return to Wall Street.

Stocks on Wall Street slid on Monday, with the S&P 500 dropping by the most in over two months, as an upcoming speech by Jerome H. Powell, the Federal Reserve chair, loomed over investors who are focused on the path for interest rates in the months ahead.

The benchmark index dropped 2.1 percent, its sharpest daily decline since June 16. The tech-heavy Nasdaq composite dropped 2.5 percent, a drop that nearly erased its gains for August.

The stock market has been reversing some of its recent rebound, gains that had been fueled by a batch of better-than-expected corporate earnings reports and a report that inflation had cooled in July. Monday’s drop followed on a small decline last week, which came on the heels of four back-to-back weekly gains that had lifted the S&P 500 by more than 17 percent.

The sudden swing shows that investors recognize they’re still not out of the woods when it comes to the Federal Reserve, recalling the sting of soaring inflation and a series of large interest rate increases by the Fed this year that helped push stock prices sharply lower. The inflation reading for July, which showed that gains in consumer prices steadied from the month before, had spurred hopes that the central bank might ease off its campaign to raise borrowing costs.

But it has dawned on investors that such a conclusion was premature, said Victoria Greene, chief investment officer at G Squared Private Wealth.

“People are coming back to reality that the world is still a very uncertain place,” she said.

A speech by Mr. Powell, at a gathering of central bankers in Jackson Hole, Wyo., could help clarify the Fed’s expectations for inflation. Economists will be listening for clues on whether the Fed will make another three-quarter-point increase in interest rates at its September meeting or go with a smaller half-point increase.

Monday’s trading reflected worries that policymakers might choose the more aggressive approach. Large jumps in borrowing costs help contain inflation by slowing the economy, but they also make it harder for companies to grow their businesses and more expensive for consumers to borrow and spend.

On Monday, a survey from the National Association for Business Economists showed that nearly three-quarters of corporate economists were skeptical that the Fed could reach its 2 percent inflation target in the next two years without bringing on a recession. Fifty-two percent of respondents said they were “not very confident” in the Fed’s efforts to fight inflation, and 21 percent said they were “not at all confident.”

“The concern is that the Fed is now going to go out of their way to remind people that they’re still going to hike rates,” Ms. Greene said.

The pessimistic mood on Monday affected other markets, too. Yields on government bonds rose, with the yield on 10-year Treasury notes climbing above 3 percent for the first time since July 20. The yield on 2-year notes jumped to 3.32 percent.

The price of Bitcoin, the largest cryptocurrency, fell more than 2 percent to $21,084. The cryptocurrency is down more than 54 percent since the beginning of the year.

In Europe, the Stoxx 600 fell close to 1 percent leaving the overall index down over 22 percent since the start of the year. The drop came as the price of natural gas in Europe surged more than 14 percent after Gazprom, Russia’s state-owned energy company, announced that the Nord Stream 1 pipeline, a major supplier of natural gas to Europe, would halt production for three days starting Aug. 31.

Hong Kong’s Hang Seng fell about 0.6 percent and Tokyo’s Nikkei 225 dropped around 0.5 percent.

China’s central bank on Monday said it was cutting its five-year interest rate by 0.15 percentage points, to 4.3 percent, a moved that could bolster the country’s real estate sector. The central bank also said it was reducing a one-year interest rate by 0.05 percentage points, to 3.65 percent.