WASHINGTON (AP) — The leaders of the central banks of four major economies are expressing alarm that multiple trade conflicts are threatening to slow global growth.

The officials say the escalating trade fights involving the United States, China and Europe could erode business confidence, lead companies to delay investment and hurt the global economy. The central bank leaders add, though, that so far there's scant evidence that this has happened yet.

"What's the effect on confidence?" European Central Bank President Mario Draghi says at a conference in Portugal. "What's the effect on business investment? There are lessons from the past, and they are all very negative."

Federal Reserve Chairman Jerome Powell notes that the Fed has heard of businesses postponing investment and hiring, and "those concerns seem to be rising."