Fiscal 2015 budget requests from all ministries and agencies are likely to top ¥101 trillion, the highest ever, sources said.
Growing social security expenses are responsible for swelling requests for the general account budget, which totaled ¥99.25 trillion for this fiscal year.
The requests point to the difficulty faced by Prime Minister Shinzo Abe's administration in trying to restore the government's fiscal health, already the worst among major developed economies.
The Finance Ministry has asked ministries and agencies to submit their requests by Friday.
The administration did not put a ceiling on budgetary requests for fiscal 2015 because tax revenue can't be projected until a decision is made on whether to go ahead with a consumption tax hike to 10 percent in October next year, from 8 percent now.
Total policy spending requests, including for social security, defense, industrial development and public works projects, are expected to reach about ¥76 trillion, the sources said Tuesday.
The administration also plans to earmark around ¥3.9 trillion to implement its economic growth strategy aimed at boosting the corporate sector and local economies.
Interest payments and other debt-servicing costs are expected to expand to about ¥26 trillion, up by more than ¥2 trillion from the fiscal 2014 budget, the sources said.
The Health, Labor and Welfare Ministry is expected to request ¥31.67 trillion, topping ¥30 trillion for the third straight year, and the Defense Ministry a record ¥5.05 trillion, including money for U.S. military realignment costs.
The budget sought by the Land, Infrastructure, Transport and Tourism Ministry is expected to increase to ¥6.69 trillion as it plans to bolster disaster prevention.
The budget is usually drafted in December for the next fiscal year starting in April.