Japan's economic deterioration has slightly eased, mainly due to increased public works spending, but a self-sustained recovery of the private sector has yet to develop, Bank of Japan Gov. Masaru Hayami said Thursday.

Citing the central bank's monthly report of recent economic and financial developments for December, released the same day, Hayami told a news conference, "the economic deterioration in Japan has moderated somewhat, mainly due to the increase in public investment."

The December report omits a phrase the central bank has been using in the past several reports describing Japan's economic conditions as continuing to deteriorate.