TOKYO, Feb 5 (Reuters) - Japanese government bonds rose on Tuesday, with the benchmark yield backing off a three-week high hit in the previous session after weak U.S. data and fears about the impact of political woes in Europe whetted investor appetite for safe-haven debt. * But supply concerns capped gains, as the Ministry of Finance offered 2.4 trillion yen ($26 billion) of 10-year notes, reopening the current issue with a coupon of 0.8 percent. The ministry increased the monthly offering amount by 100 billion yen this month, and will do the same next month, to fund its supplementary budget. * Most market participants said the sale would go smoothly, after the benchmark yield moved away from a six-week low of 0.720 percent hit last month. * "With intermediate JGB yields declining on expectations of monetary easing and superlong JGB yields coming under upward pressure in anticipation of the new administration's reflationary policies, the 10-year JGB yield has gradually become neutral relative to the curve," strategists at Bank of America Merrill Lynch said in a note to clients. * The 10-year JGB yield slipped half a basis point to 0.800 percent, while the 10-year JGB futures contract ended morning trade up 0.15 point at 143.83. * "With the end of the fiscal year approaching at the end of next month, some investors who have been holding off, hoping to buy at better yield levels, might decide to buy at this auction after all," said a fixed income fund manager at a European asset management firm. * Spanish and Italian bond yields rose in the previous session, after political worries heightened investors' fears that those countries would be able to maintain their commitment to solving their debt problems. U.S. Treasuries climbed on these concerns, as well as disappointing U.S. factory orders data and a downward revision to a report on U.S. business investment plans. * The 20-year yield was flat at 1.795 percent, while the 30-year bond yield lost half a basis point to 2.000 percent. * On Monday, the chairman of Japan's Government Pension Investment Fund told Reuters in an interview that the fund would review its portfolio allocation model around April, as yields on 10-year JGBs were languishing at around 0.8 percent. GPIF is the world's biggest public pension fund, with its assets of $1.2 trillion mostly held in JGBs.