Inflation has shown signs of moving back toward the Fed’s 2 percent goal, and consumer spending, the job market and overall growth have remained resilient so far. But Mr. Trump’s trade war is denting business investment and exacerbating a manufacturing slowdown, and it is unclear how — or whether — it will be resolved. The United States and China are expected to meet again next month, and both sides have taken steps before that meeting to ease their trade fight. But a deal is not guaranteed, and Mr. Trump plans to impose tariffs on nearly all Chinese imports by the end of the year if one is not reached.

Adding to the mixed economic picture: Household confidence is wobbling, and the global economic picture is tenuous. Germany, Europe’s largest economy, is on the brink of recession, and Britain is grappling with its contentious exit from the European Union.

“The consumer is doing well, but there are other parts of the economy that aren’t doing well: manufacturing being the obvious one, but business investment is weak, and foreign demand is weak,” said Michael Feroli, the chief United States economist at J. P. Morgan, who expects policymakers to cut rates one more time this year. “I don’t necessarily think they have a plan to go again, but I think the economy will continue to look a little soft.”

A strike on a Saudi Arabian oil facility over the weekend could further complicate the picture. It will at least temporarily disrupt oil supplies and affect prices, though many experts say a severe shock to consumers is unlikely. Still, it opens the door to intensified geopolitical tension.

Heightening Mr. Powell’s communications challenge, the Fed will release new economic projections after the meeting for the first time since June. That means the Fed chair will have to knit his 16 colleagues’ interest rate projections into one comprehensive narrative.