May 8 (Bloomberg) -- Japan's Financial Services Agency has called on major banks to disclose details of assets and losses related to subprime mortgages before they announce full-year earnings, Nikkei English News reported, without saying where it got the information.

The Japanese financial regulator has asked banks that hold collateralized debt obligations to provide asset balances for the subprime-related portions as well as details on guarantees attached to their holdings, the news service said.

Life and non-life insurance companies would supply the information by the time they report earnings for the first half of the year, Nikkei said. The FSA also plans to ask major brokerages that have already released full-year financial statements to make disclosures when they post first-quarter results, Nikkei said.

The FSA will use disclosure guidelines compiled by the Financial Stability Forum, which consists of monetary authorities from Japan, the U.S. and Europe, the news service reported. The FSA may take steps to urge improvements if financial institutions fail to comply, Nikkei said.

To contact the reporter on this story: Yi Tian in New York at ytian8@bloomberg.net.

Last Updated: May 8, 2008 14:16 EDT