TOKYO, May 6 (Reuters) - Japanese government bond (JGB) yields rose on Friday after a sell-off in U.S. Treasuries overnight, while the 10-year bond yields were flat as the Bank of Japan continued its daily offer to buy unlimited amounts of the bonds.

The 20-year JGB yield rose 2 basis points to 0.770%. The 30-year JGB yield also rose 2 bps to 1.005%.

U.S. Treasury yields rose overnight, as traders questioned the Federal Reserve's ability to keep the economy from falling into recession, with data pushing markets to price in a more aggressive monetary policy.

"Japanese bond yields were under pressure from the upward trend of overseas rates. Although the BOJ maintains its loose monetary policy, there is a speculation that it would tighten its policy eventually," said a market participant at a foreign brokerage.

The 10-year JGBs were untraded and the yield remained at 0.225%.

The Japanese central bank continued its offer to buy unlimited amounts of the 10-year government bonds to defend its upper limit of the yield target.

Yields on shorter-ended notes also rose, with the two-year JGB yield up 0.5 bp at -0.050% and the five-year yield climbing 1 bp to 0.020%.

The 40-year JGBs were not traded and the yield was flat at 1.080%.

(Reporting by Tokyo markets team; Editing by Subhranshu Sahu)