TOKYO, Nov 10 (Reuters) - Japanese government bond futures inched down on Tuesday as an agreement by the Group of 20 to keep stimulus in place boosted U.S. and Japanese stocks, but losses were limited after investors saw the U.S. Treasury market comfortably handle a record-sized note auction.

* Focus was on the 300 billion yen ($3.3 billion) 40-year JGB auction on Tuesday. The market expects the sale to draw enough demand from regular buyers of superlong bonds such as domestic life insurers and pension funds. The relatively small offer amount is also expected to expected to make it easier for the market to absorb the issue.

* JGB participants will not be breathing a big sigh of relief even if the 40-year sale proceeds smoothly, as Thursday's 2.4 trillion yen five-year tender will present a sterner test to a market that has recently seen a string of lacklustre auctions.

* The JGB market has been hounded by supply concerns for the past month as it braces for issuance increases to offset low demand for retail bonds, fund an expected tax revenue shortfall and help finance the country's spending plans for next fiscal year.

* December 10-year JGB futures 2JGBv1 declined 0.02 point to 137.36, confined to a tight 0.12 point range.

* The five-year yield JP5YTN=JBTC was flat at 0.715 percent while the benchmark 10-year yield JP10YTN=JBTC edged up 1 basis point to 1.480 percent, a fresh five-month high.

* U.S. Treasuries were steady to modestly higher on Monday following strong demand for a record-sized three-year note sale. [US/]

* Tokyo's Nikkei average .N225 climbed 1.4 percent. [.T]

(Reporting by Shinichi Saoshiro; Editing by Michael Watson)