Big Banks Set Aside Billions as They Brace for a Downturn

America’s biggest banks issued warnings on Friday of economic malaise on the horizon, even as some reported better-than-expected profits.

JPMorgan Chase, the nation’s largest bank, raised the risk of a “mild recession” to arrive later this year. Jamie Dimon, the bank’s chief executive who is normally one of the more gregarious Wall Street figureheads, repeatedly demurred from hard-and-fast predictions on a call with reporters.

“We don’t know the future,” he said. “There are all these geopolitical uncertainties which are real, and we have our eyes focused on it. They may...