In separate speeches, Governor Michelle Bowman and Boston Federal Reserve President Susan Collins said there was still a possibility that the U.S. Federal Reserve would be forced to raise interest rates further if economic data did not show an improvement in inflation.

Bowman's comments were even more explicit because she noted that progress on monetary tightening so far has not been enough to bring inflation down to the Federal Reserve's target of 2 percent.

"I still expect that there is likely to be a need for further rate hikes to bring inflation back to 2 percent in due course," she said in prepared remarks to a group of bankers.

With a majority of FOMC members expecting inflation to remain above target until at least 2025, and expecting that a cut against inflation will be slow, Bowman believes that further tightening of monetary policy will be needed.

For her part, Collins said the recent inflation data has been encouraging even though it is "too early" to declare victory over it, while core inflation remains high.

The US Federal Reserve kept interest rates unchanged during its meeting a few days ago, but hardened its stance on monetary tightening, as it is expected to raise interest rates again by the end of the year, and tighten monetary policy until 2024 more than previously expected.

The central bank said in a statement that the Federal Open Market Committee's decision to keep the key lending rate between 5.25 percent and 5.50 percent gives officials time to "assess additional information and its implications for monetary policy."

The Federal Reserve said on Wednesday that economic activity was expanding at a "robust pace," citing rising jobs and a drop in unemployment.