The benchmark 10-year JGB futures contract eased 3 ticks to 143.82, moving back toward a 2-1/2-month low of 143.27 hit on Aug. 16.
Futures held above technical support at their 14-day moving average, now at 143.72. But volume was only 17,897 contracts, sharply below last week's average of 29,250 contracts .
The 10-year yield added 0.5 basis point to 0.810 percent.
Benchmark yields dropped to a one-week low of 0.800 percent last Thursday following lacklustre demand at a 20-year sale.
US Federal Reserve Chairman Ben Bernanke will speak on Friday at an annual central bank event in Jackson Hole, Wyoming, after he cited "scope for further action" in a letter to a congressional oversight panel last week.
Investors will be listening closely for hints on the likelihood and timing of a third round of quantitative easing, or QE3, which would bolster Treasuries and in turn give support to JGBs.
"JGBs are more sensitive to macro factors," said Le Ngoc Nhan, a strategist at Morgan Stanley MUFG, who expects the 10-yield to rise to 0.900 percent by the end of this quarter.
"I remain cautiously short in the form of put options," he added.
Superlong bonds were also weaker, with both the 20- and 30-year debt up 0.5 basis point, at 1.670 and 1.885 percent respectively.
Yields on the 20-year bonds have moved up six basis points so far this month, while that on the 30-year debt are up 7.5 basis points.
"The sell-off in the JGB market has also driven by the somewhat brighter than expected US economic numbers during August and the talk of aggressive measures for the ECB," said Tomohisa Fujiki, interest rate strategist at BNP Paribas in Tokyo.
"As these things have not settled yet, market participants' eyes are on what's going to be delivered from these events (Jackson Hole and ECB's September meeting). JGB should stay a little bit firm in the next few weeks."
Month-end duration extension by life insurers and pension funds often helps the yield curve flatten in the final trading days of a month, as such buyers snap up longer maturities to extend the duration of their portfolios.
Such buying had yet to emerge as of last week, when the spread between the 10-year and 30-year yields stood at 1.075, its widest since late June and up from 0.980 five weeks earlier. The spread between 10-year and 20-year yields rose to 0.875 last Thursday, its highest since December 2010.
"Normally, August is a month when we see a lot of extension coming in because September is a redemption month, so we might see demand, but I never trust seasonality," said Nhan at Morgan Stanley MUFG.