TOKYO, June 25 (Reuters) - Japanese government bond

yields ticked higher for a fourth straight session on Tuesday,

as investors positioned for a looming reduction in the Bank of

Japan's bond buying.

Investors were also cautious amid uncertainty over future

bond supply, following recent reports that the finance ministry

may shorten the average maturity of JGB issuance.

A smooth auction of 20-year JGBs on Tuesday helped to cap

the rise in yields.

The 20-year JGB yield added 1.5 basis points

(bps) to 1.84% as of 0605 GMT, while 30-year yield

also rose 1.5 bps to 2.19%.

The 10-year yield was 1 bp higher at 0.995%.

Benchmark 10-year JGB futures finished the day down

0.1 yen at 143.48.

The BOJ is due to reveal its plans for a tapering of its

massive monthly bond buying programme, known locally as rinban,

at the conclusion of its next policy meeting on July 31. The

central bank has also kept the door open to an interest-rate

hike at the same gathering.

"Long-end yield are poised to gradually rise until we get a

clearer picture of what's going to happen with supply and

rinban," said Shoki Omori, chief Japan desk strategist at Mizuho

Securities.

"There are not many investors involved in the longer end, so

volatility there is going to rise."

The five-year JGB yield rose 0.5 bp to 0.545%,

while the two-year yield fell 0.5 bp to 0.295%.