TOKYO, April 20 (Reuters) - Yields on longer-dated Japanese government bonds fell on Tuesday, after an auction of 20-year notes drew reasonably strong demand, easing concerns about investor appetite for new debt coming to market. The lowest price accepted at the finance ministry’s auction of 20-year bonds was higher than traders’ expectations, which is an indication of healthy demand, according to a bond analyst. Japanese investors are also watching an auction of U.S. 20-year Treasuries on Wednesday, as it will be an important test of global appetite for fixed income, traders said. If the Treasury auction goes well, bond yields could continue to fall in major economies, traders said. However, a disappointing auction could cause yields to spike higher, they added. Benchmark 10-year JGB futures fell 0.06 point to 151.37, with a trading volume of 16,316 lots. The 10-year JGB yield was flat at 0.080%. The 20-year JGB yield fell 1 basis point to 0.435%, and the 30-year JGB yield fell 1 basis point to 0.640%. At the long end of the curve, the 40-year JGB yield fell 1.5 basis points to 0.675%. The five-year yield rose 0.5 basis point to minus 0.095%, but the two-year JGB yield was unchanged at minus 0.135%. (Reporting by the Tokyo markets team; Editing by Rashmi Aich)