Stocks in the United States ended a choppy session lower after two Federal Reserve speakers emphasized the central bank's determination to remain patient until price pressures return to levels consistent with its 2% target.

The S&P 500 fell 0.9%, capping a two-day rally. The Nasdaq 100 also fell. Treasury yields have risen, with the 10-year yield hovering around 3.87%.

Fed vice chair Lael Brainard temporarily lifted sentiment when she said during an event in Washington that the central bank should slow its rate hikes "soon." She did, however, emphasize that the Fed had "additional work to do" to reduce inflation, which kept some investors on edge. Brainard did not expressly commit to a half-point hike in December, nor did she explain what she meant by "soon."

Earlier, markets were rattled by Fed Governor Christopher Waller's hawkish remarks, as investors pondered whether the post-CPI euphoria was overblown.