Japan's top currency official warned against delays in efforts to improve the nation's finances as Prime Minister Yoshihiko Noda grapples with the world's biggest public debt burden.

Advanced economies such as Japan "cannot postpone fiscal consolidation efforts forever," Takehiko Nakao, 56, vice finance minister for international affairs, said in an interview in his office in Tokyo on Tuesday.

Noda faces opposition in the Diet and within his Democratic Party of Japan as he seeks to double the consumption tax by 2015 to boost revenue, highlighting the risk that policy initiatives will stall. The government must quickly overhaul the tax and social security systems to prevent borrowing costs from spiraling in the next decade, Yasuhiro Sato, chairman of the Japanese Bankers Association, said last month.