TOKYO, Aug 25 (Reuters) - Yields on benchmark 10-year Japanese government bonds rose on Wednesday, tracking the strength in U.S. Treasury yields, while investors stayed on the sidelines ahead of a key speech by Federal Reserve Chair Jerome Powell later this week. The 10-year JGB yield rose 0.5 basis point to 0.020%, while 10-year JGB futures fell 0.03 point to 152.23, with a trading volume of 13,123 lots. Powell is due to speak at the Fed’s annual economic symposium at Jackson Hole, Wyoming. Worries the Fed was edging closer to tapering its stimulus weighed on global markets last week, but investors are now much less confident Powell’s speech will indicate a timeline for winding down the Fed’s bond-buying programme. Yields on most securities were unchanged, with the 20-year JGB yield flat at 0.405%, while the two-year JGB yield and the five-year yield at minus 0.140% and minus 0.120%, respectively. The 40-year JGB yield was also unchanged at 0.725%. The 30-year JGB yield fell 0.5 basis point to 0.645%. (Reporting by Tokyo markets team, Editing by Sherry Jacob-Phillips) Our Standards: The Thomson Reuters Trust Principles.