TOKYO, June 18 (Reuters) - Japanese government bond (JGB) yields slid on Friday, tracking an overnight retreat in U.S. Treasury yields, while the Bank of Japan announced an extension of its pandemic-relief programme. The 10-year JGB yield fell 0.5 basis points to 0.055%, while the 20-year JGB yield declined 1.5 basis points to 0.430%. The 30-year JGB yield sank 1 basis point to 0.675% and the 40-year JGB yield dropped 1.5 basis point to 0.730%. Two-year and five-year debt were untraded in the early afternoon. Benchmark 10-year JGB futures added 0.07 point to 151.60. “U.S. yields that rose after the FOMC meeting are now retreating, so the feeling is spreading that it’s ok to buy,” said Makoto Suzuki, a senior debt strategist at Okasan Securities. “It looks like a strong sense of stasis will return to the yen bond market.” Ten-year U.S. Treasury yields were at 1.5158% on Friday, after rising as high as 1.5940 in the previous session after the U.S. Federal Reserve brought forward projections for interest rate hikes. On Friday, the BOJ maintained its yield curve control targets set at -0.1% for short-term interest rates and around 0% for 10-year bond yields. It also extended by six months the September deadline for its pandemic-relief programme, as widely expected. (Reporting by Tokyo Markets Team; Editing by Aditya Soni) Our Standards: The Thomson Reuters Trust Principles.