WASHINGTON—The Federal Reserve on Wednesday said it will begin trimming its monthly bond purchases in November with plans to end them in 2022, but held to its belief that high inflation would prove “transitory” and likely not require a fast rise in interest rates. However, the U.S. central bank nodded to global supply difficulties as adding to inflation risks, saying that those factors “are expected to be transitory,” but would need to ease to deliver the anticipated drop in inflation. “As the pandemic subsides, supply-chain bottlenecks will abate and job growth will move back up,” Fed Chair Jerome Powell said in a news conference after the release of the central bank’s latest policy statement. “And as that happens, inflation will decline from today’s elevated levels. Of course, the timing of that is highly uncertain.” In its statement following the end of a two-day meeting, the Fed said that in light …