* Ten-year futures up slightly in 2nd lowest volume this year
* Five-, 10-year yields unchanged
TOKYO, Aug 26 (Reuters) - Yields on Japanese government bonds were steady on Monday ahead of a 1.2 trillion yen ($12.2 billion) auction of 20-year debt the following day.
Apart from Tuesday's auction, the Ministry of Finance is to sell 2.9 trillion yen of two-year bonds on Thursday.
The 20-year yield was unchanged at 1.700 percent after earlier adding 0.5 basis point to 1.705 percent to match a two-week high hit on Friday.
"The absolute level of yield is OK but not very attractive, but not very unattractive. It should be OK just slightly above 1.7 percent," said Yuya Yamashita, rates strategist at JPMorgan in Tokyo. "The relative value is supportive. There is no other relative value player in the superlong sector."
The 30-year yield dipped 0.5 basis point to 1.810 percent, while both the five-year and 10-year yields were flat, at 0.300 and 0.760 percent, respectively.
Ten-year futures were up 0.04 point at 143.75, facing resistance at their 20-day moving average of 143.84. Trading volume was light, with 11,970 contracts changing hands, the second lowest this year.
Bank of Japan Governor Haruhiko Kuroda said on Saturday that the bold policy actions that he has championed to spur growth in the world's third-largest economy were gaining traction.
The BOJ stunned financial markets in April by promising to inject $1.4 trillion into the economy in less than two years.
"While we expect 20-year cheapness to continue as long as the BOJ maintains its current purchase-operations format, the yield is trading at a level that favours a short-term rebound on the curve," Royal Bank of Scotland wrote in a note.