The New York Stock Exchange opened in positive territory. But in a speech in Wyoming, Warsh then hinted that a key interest rate hike could soon be on the horizon in the US - and investors lost heart.
At the close, the Dow Jones Industrial Average was unchanged, while the broad S&P 500 index fell 0.3 percent and the tech-heavy Nasdaq Composite Index fell 0.5 percent.
Another problem is that interest rates on long-term US bonds continue to rise stubbornly, which is linked in part to the country's record-high national debt.
Five of the big tech companies - Google owner Alphabet, Amazon, Apple, Facebook owner Meta and Microsoft - went against the grain and rose.
Over the week as a whole, the Dow rose 0.6 percent, the S&P 500 index 0.5 percent and the Nasdaq 0.9 percent.
