By Kevin Buckland
TOKYO, Sept 17 (Reuters) - Japanese government bonds (JGBs) rose slightly on Wednesday, supported by robust demand at an auction of 20-year debt, even as investors kept a cautious eye on a crucial U.S. interest rate decision later in the day.
The 10-year JGB ticked up, sending its yield JP10YTN=JBTC down 0.5 basis point (bp) to 1.6%, after the finance ministry published the results of the 20-year bond sale. A gauge of demand, called the bid-to-cover ratio, jumped to its highest level since May 2020.
The five-year yield JP5YTN=JBTC also declined 0.5 bp to 1.15%.
Yields move inversely to prices.
Investors had been watching the auction closely because a lack of buyers for the longest-dated JGBs meant the 20-year yield JP20YTN=JBTC climbed as high as 2.69% at the start of the month, a level not seen since October 1999.
The 30-year yield JP30YTN=JBTC had soared to an unprecedented 3.285% earlier this month.
In addition, markets are concerned about Japan's fiscal health, with the ruling party choosing a new leader after fiscally hawkish Prime Minister Shigeru Ishiba stepped down following a bruising election defeat.
Other cash JGBs were yet to trade after the auction results, but the benchmark 10-year JGB futures 2JGBv1 extended earlier gains to be up 0.12 yen at 136.64 yen as of 0350 GMT.
"These metrics confirm that investor appetite for long-dated JGBs remains intact despite the prevailing environment of policy uncertainty," said Shoki Omori, chief desk strategist at Mizuho Securities.
"The 20-year sector is steadily evolving into a nexus for a variety of market participants, including domestic banks, life insurers, and overseas investors."
On the day, the 20-year yield fell 0.5 bp to 2.665% in early trading, while the 30-year was flat at 3.25%.
The two-year yield was steady at 0.875% at the midday trading recess.
Japanese yields were already being pulled lower by declines in U.S. yields overnight, with traders shoring up bets for a series of rate cuts from the Federal Reserve, ostensibly beginning with a 25-bp reduction later in the day.
Market-implied odds signal at least two quarter-point cuts by year-end, and 96 basis points of reductions by end-March.