TOKYO, July 21 (Reuters) - Long-dated Japanese government bond (JGB) prices eased on Wednesday tracking U.S. peers ahead of a long weekend as Japan gears up for the Olympics, officially starting later in the week. Benchmark 10-year JGB futures fell 0.06 point to 152.4, with a trading volume of 21,468 lots. ADVERTISEMENT The 20-year JGB yield rose 1 basis point to 0.400% while the 30-year yield rose 1.5 basis points to 0.655%. The 40-year JGB yield rose 2 basis points to 0.735%. But the 10-year bond bucked the trend, with the benchmark 10-year cash JGB yield falling 0.5 basis point to 0.005%. U.S. bond yields rebounded from five-month lows on Tuesday after the previous session’s biggest single-day decline since February. Reporting by Tokyo Markets Team; editing by Vinay Dwivedi Our Standards: The Thomson Reuters Trust Principles.