TOKYO, July 15 (Reuters) - Japanese government bond yields fell on Thursday in sympathy with a decline in U.S. Treasury yields, with 20-year JGB yields sinking to an almost seven-month low. Sentiment was also helped at the margin by a well-received sale of three-month T-bills and a smooth liquidity-enhancing auction of JGBs with between one- and five years left to maturity. The 20-year JGB yield dropped 1.5 basis points to 0.385%, the lowest level since Dec. 25, while the 10-year JGB yield declined 0.5 basis point to 0.010%. Benchmark 10-year JGB futures rose 0.04 point to 152.34, with a trading volume of 13,683 lots. Ten-year Treasury yields dropped as low as 1.3290% in Asia following a 6.58 basis-point slide overnight after Federal Reserve Chair Jerome Powell shrugged off evidence of heated inflation this week to say that a tapering of stimulus is “still a ways off.” The 30-year JGB fell 1.5 basis points to 0.650%, while that on the 40-year JGB declined 1 basis point to 0.730%. The two-year JGB yield was flat at minus 0.130%, and the five-year yield was unchanged at minus 0.125%. (Reporting by Tokyo markets team; Editing by Shailesh Kuber)