President Trump has never been shy about criticizing the Federal Reserve, frequently seeking to pressure the nation’s central bank into reducing interest rates more swiftly.

“Interest Rates should be lowered, something which would go hand in hand with upcoming Tariffs!!!,” Mr. Trump posted on Truth Social last monthadding: “Lets Rock and Roll, America!!!”

But the Fed is expected to see things differently on Wednesday — choosing to hold rates steady in the face of rising prices and slowing growth — in a move that seems destined to stoke Mr. Trump’s anger.

At the heart of the tension are Mr. Trump’s tariffs, which he has promised to apply more expansively beginning April 2. The White House contends its protectionist policies can rejuvenate American manufacturing and reduce the country’s reliance on imports, but economists believe that Mr. Trump risks touching off a protracted global trade war that will badly harm the U.S. economy.

The latest dour projection arrived Tuesday, when Fitch Ratings cut its U.S. growth forecast for this year to 1.7 percent from 2.1 percent. It explicitly pointed to Mr. Trump’s tariffs — and the “huge uncertainty” around them — as two of the drivers behind a potential economic slowdown and short-term rise in prices.

The uncertainty is likely to freeze any rate cutting at the Fed, perhaps straining an already tortured relationship between Mr. Trump and Jerome H. Powell, the man he handpicked to serve as chair of the central bank in 2017.

In his first term, the president described Mr. Powell as the “enemy,” and blasted his colleagues as “boneheads,” in a bid to browbeat the Fed into slashing interest rates. Mr. Trump at one point even considered firing Mr. Powell, raising fears that the White House might try to undermine the Fed’s political independence.

Soon after returning to the White House, the president revived his attacks: He said, again, that he would “demand that interest rates drop immediately,” and one of his leading advisers — the tech billionaire Elon Musk — signaled support for an audit of the central bank. When the Fed chose to hold rates steady at its last meeting, Mr. Trump charged anew that Mr. Powell and the Fed had “failed to stop the problem they created with inflation.”

“If the Fed had spent less time on DEI, gender ideology, ‘green’ energy, and fake climate change, Inflation would never have been a problem,” Mr. Trump wrote in a post on Truth Social.