Federal Reserve policymakers will have a "robust debate" about cutting U.S. interest rates by a half percentage point at their next policy meeting in September, St. Louis Federal Reserve Bank President James Bullard said on Friday.

The Fed cut rates by a quarter point at its July policy review although the minutes of that meeting showed a couple OF policymakers favored a 50 basis point reduction.

Bullard said there would be a hardy discussion about a steep cut next month.

"I think there will be a robust debate about 50," he said in an interview with Bloomberg TV. "I think it's creeping onto the table."

Bullard said a key reason for further rate cuts is the Treasury yield curve, which recently inverted again.

"The yield curve is inverted here. We've got one of the higher rates on the yield curve here. That's not a good place to be," Bullard told CNBC in a separate interview.

Bullard had said last week that he was not ready to commit to reducing rates at the Fed's upcoming Sept. 17-18 meeting.