(Updates with results from 20-year auction)

By Rocky Swift

TOKYO, Nov 19 (Reuters) - Japanese government bonds

(JGBs) slid on Wednesday, sending benchmark yields to a 17-year

high, as concerns swirled about the size of Prime Minister Sanae

Takaichi's stimulus package.

The 10-year JGB yield rose 1.5 basis points

(bps) to 1.76%, and earlier reached 1.775%, the highest since

June 2008. Yields move inversely to bond prices.

JGBs recovered some losses after the results of an auction

of 20-year securities showed investors weren't abandoning the

super-long sector.

A ruling-party panel proposed on Tuesday compiling a

supplementary budget exceeding 25 trillion yen ($160.86 billion)

to fund Takaichi's stimulus plan. That would be much larger than

the previous year's extra budget of 13.9 trillion yen.

"The clear upward trend in ultra-long-term interest rates

this week is likely driven not only by caution ahead of the

20-year auction but also by concerns about a further upward

revision in the scale of fiscal expansion," Mizuho Securities

chief bond strategist Noriatsu Tanji wrote in a note.

A sale of about 800 billion yen in 20-year JGBs by the

Ministry of Finance had a bid-to-cover ratio of 3.28, down from

the previous sale but around the average over the past year.

Even so, the so-called tail of the auction, which measures

the difference between the average and lowest prices, was 0.31,

the worst reading since the sale in May.

The 20-year yield rose 1 bp to 2.795% after

touching the highest since 1999 in the previous session. The

30-year yield was flat at 3.310%, recovering from

an earlier increase to a near-record of 3.34%.

The two-year yield rose 1 bp to 0.93%, and the

five-year yield rose 1.5 bp to 1.265%.

($1 = 155.4100 yen)