Horst Koehler, managing director of the International Monetary Fund, on Tuesday urged Japan's likely new leader Junichiro Koizumi to promote restructuring of the nation's corporate and banking sectors in "a more ambitious and expeditious" manner.

The Japanese economy will show "some growth" this year but further efforts are necessary to pull it out of a "critical phase of sluggish growth," Koehler said.

Koehler said policy debates during the leadership race of the ruling Liberal Democratic Party clarified a "need for a more ambitious and expeditious restructuring of Japan's corporations and banks."

"I do think restructuring corporations and banks is issue No. 1, No. 2 and No. 3" for Japan, the IMF chief said in a meeting with reporters ahead of a series of international financial meetings opening in Washington this weekend.