TOKYO, Oct 17 (Reuters) - Longer-dated Japanese government bonds firmed on Tuesday after a 20-year debt auction drew ample investor demand and allowed the market to deflect negative pressure from weaker U.S. Treasuries and higher stocks.
The 20-year and 30-year JGB yields were unchanged at 0.590 percent and 0.875 percent, respectively.
The bid-to-cover ratio, a gauge of demand, at Tuesday's 1 trillion yen ($8.92 billion) 20-year JGB auction was 4.05 - well over 3.85, the average from the past 12 sales.
The finance ministry auctions 20-year JGBs every month.
The good demand for the 20-years auctioned on Tuesday reflected the market taking some comfort from media polls showing Prime Minister Shinzo Abe's ruling party holding the lead ahead of lower house elections on Sunday.
The financial markets expect the Bank of Japan to retain its massive debt-buying monetary easing scheme if Abe's ruling party retains power.
The benchmark 10-year yield edged up 1 basis point to 0.070 percent.
U.S. Treasury yields rose on Monday after a report that President Donald Trump was favouring Stanford economist John Taylor to head the Federal Reserve and weekend comments from incumbent Fed Chair Janet Yellen extolling the strength of the economy. ($1 = 112.0700 yen) (Reporting by the Tokyo markets team; Editing by Eric Meijer)