Most strategists expect the Fed to refrain from a third round of quantitative easing, known as QE3, though the central bank is expected to emphasize its commitment to maintaining easy policy and could signal that further stimulus steps are forthcoming.

Investors are divided on the possible outcome of a European Central Bank meeting on Thursday. If the ECB embarks on bond buying, that could fuel investors' risk appetite and trigger JGB selling, whereas an interest rate cut might have the opposite market reaction.

"Gains will likely be limited ahead of tomorrow's 10-year auction," said a fixed-income fund manager at a Japanese asset management firm. "The market is positioned for uncertainty again ahead of the Fed and the ECB."

Some investors are likely to sell 10-year bonds as they look to make room on their books ahead of a 2.3 trillion yen ($29.4 billion) auction in the maturity on Thursday.

Ten-year JGB futures ended morning trade up 0.018 point at 144.18, rising after four straight sessions of falls that marked its longest losing streak since November. They remain below their 14-day moving average, now at 144.37.

The 10-year cash bond yield skidded 1.5 basis points to 0.775 percent, but still remained above a nine-year low of 0.720 percent hit last month.

Yields in the superlong tenor also fell from three-week highs touched in the previous session, with the 20-year yield giving up two basis points to 1.590 percent and the 30-year yield falling 1.5 basis points to 1.795 percent.