U.S. President Donald Trump slammed Federal Reserve Chairman Jerome Powell after the central bank's latest interest rate decision, saying the Fed chief "let us down."

As expected, the Fed lowered its benchmark federal funds rate by 25 basis points during its July meeting and moved up the end date for its quantitative tightening program, through which the Fed has been slimming its $3.8 trillion balance sheet.

But stocks dropped after Powell told reporters the rate cut was a "mid-cycle adjustment" rather than the start of a lengthy easing cycle, although he did not close the door on another rate cut in 2019.

The S&P 500 index fell 1.09% to 2,980.38 at the end of the day as investors saw decreased chances that the Fed will ease policy again this year.

"What the Market wanted to hear from Jay Powell and the Federal Reserve was that this was the beginning of a lengthy and aggressive rate-cutting cycle which would keep pace with China, The European Union and other countries around the world," Trump said in a tweet later in the afternoon.

"As usual, Powell let us down, but at least he is ending quantitative tightening, which shouldn't have started in the first place," he added.