Japanese government bonds hold steady after tumultuous week

TOKYO, Aug 25 (Reuters) - Japanese government bonds steadied on Monday after a tumultuous week that saw fiscal concerns drive super long-term yields to record highs.

The benchmark 10-year JGB yield JP10YTN=JBTC was flat at the 1.615% level reached on Friday, its highest since October 2008. Futures 2JGBv1 on the bonds fell 0.02 yen to 137.53.

JGBs have plunged in recent months as concerns mounted about the government's debt levels and deficit spending. Selling pressure intensified after a poor electoral showing last month for the coalition of fiscal hawk Prime Minister Shigeru Ishiba, stirring speculation that he will step down.

"Investors remain cautious due to the lack of progress in domestic politics and fiscal policy, which is leading to sluggish trading," said Katsutoshi Inadome, a senior strategist at Sumitomo Mitsui Trust Asset Management.

Yields on 30-year JGBs were unchanged from an all-time peak of 3.21% reached on Friday. The 20-year yield JP20YTN=JBTC fell 0.5 basis point to 2.660%, edging lower from the highest level since November 1999 hit in the previous session.

Most cash bonds are yet to trade in Tokyo, as of Monday afternoon. The market may have been supported by a poll showing a rebound in public approval for PM Ishiba.

Support for Ishiba's cabinet stood at 39%, surging by 17 percentage points from the previous month, a Yomiuri newspaper poll showed.

JGB yields are seeing a triple peak following a surge in late May after poor demand at auctions and again in July in the run-up to Japan's upper house elections. The recent jump in 30-year yields may compel speculators to add to short positions on JGB futures, said IG market analyst Tony Sycamore.

"If the break above 3.20% is confirmed, a move to 3.4% looks to be achievable in the months ahead," he said.