The Ministry of Finance (MOF) is considering increasing the issuance of 30- and 40-year Japanese government bonds by a total of 2 trillion yen ($17 billion) in the new fiscal year starting in April, government officials with knowledge of the matter said on Wednesday.

The plan is aimed at taking advantage of current ultra-low yield levels to reduce the need for future debt rollovers as Japan's public debt continues to snowball.

The ministry is also likely to reduce issuing short-term debts instead, such as two- and five-year notes, and to trim the total debt issue from 155.1 trillion yen planned for the current fiscal year, they added.

The MOF is contemplating an increase of around 1 trillion yen each in the issuance of 30- and 40-year JGBs and plans to float the idea when ministry officials meet primary dealers on Friday before making a final decision, the sources said.

In the current fiscal year to March, the ministry plans to sell 1.6 trillion yen of 40-year bondsand 8.0 trillion yen of 30-year bonds, both record amounts.

Still, the 30-year JGB yield stood at 1.445 percent JP30YTN=JBTC, way below the country's inflation levels. Japan's core consumer price inflation was 3.0 percent in September, or an estimated 2.0 percent when the effect of a sales tax hike is excluded.

Yields on 30- and 40-year bonds have fallen sharply since the Bank of Japan stepped up buying in these maturities following its surprise easing on Oct 31.

The MOF's plan came as Prime Minister Shinzo Abe announced on Tuesday he would postpone a planned sales tax hike by 18 months to support the economy.

The move could raise concerns over whether Japan can get its public finances in shape despite Abe's pledge to stick to the government's goal to have a balanced budget excluding debt-related revenues and expenses by 2020.