A measure of future U.S. economic expansion eased modestly last week though the annualized growth rate continued to climb, a research group said on Friday.

The Economic Cycle Research Institute, a New York-based independent forecasting group, said its Weekly Leading Index edged down to 126.3 in the week ended September 28 from a revised 126.6 the previous week.

The previous week's number was originally reported as 126.7.

The index's annualized growth rate rose to 4.7 percent - its highest level since June 2011 - from 3.8 percent.

(Reporting by Leah Schnurr; Editing by Dale Hudson)