(Reuters) – U.S. central bankers will likely start a series of interest-rate cuts next week with a quarter-of-a-percentage point reduction, traders bet on Wednesday, as government data showed inflation cooled in August from a year earlier, but a measure of underlying inflation remained sticky.

Traders now see just a 15% chance of a bigger half-point rate cut at the Fed's Sept 17-18 policysetting meeting, down from about 29% before the report, after government data showed the consumer price index rose 2.5% from a year earlier, but excluding volatile food and energy prices it was up 3.2%.

(Reporting by Ann Saphir; Editing by Andrew Heavens)