Economists and investors see it as a certainty that the Fed will lower the key borrowing rate at the policy meeting July 30-31, and Powell in recent statements has moved to solidify those predictions by pointing to some concerns about economic growth and persistent weak inflation.

Central bankers have "raised concerns about a more prolonged shortfall in inflation below our 2 percent target," Powell said in a prepared speech at a Bank of France event.

And amid continued uncertainty about global growth amid rising trade tensions, Powell said inflation expectations "are near the bottom of their historical ranges."

Despite the Fed's confidence that the US economy will continue to grow, many officials feel "the combination of these factors strengthens the case for a somewhat more accommodative stance of policy."

The Fed raised the policy rate four times last year and a rate cut this month would be the first in a decade.

Powell repeated that the central bank "will act as appropriate to sustain the expansion," which after 10 years is finally reaching marginalized segments of US society.