TOKYO, June 23 (Reuters) - The yield on 10-year Japanese government bonds (JGBs) was unchanged on Wednesday, as investors awaited results of a 20-year bonds auction on Thursday, while yields on longer dated bonds tracked overnight declines in U.S. Treasury yields. The 10-year JGB yield was flat at 0.050%. The 20-year JGB yield fell 0.5 basis point to 0.425% and the 30-year JGB yield fell 0.5 basis point to 0.665%. The 40-year JGB yield also fell one basis point to 0.730%. The two-year JGB yield was unchanged at minus 0.115% and the five-year yield was also flat at minus 0.100%. Benchmark 10-year JGB futures rose 0.03 point to 151.68, with a trading volume of 12,818 lots. (Reporting by Tokyo markets team; Editing by Muralikumar Anantharaman) Our Standards: The Thomson Reuters Trust Principles.