Greg Robb - Washintgton (MarketWatch)

Japan has overtaken China as the top foreign holder of U.S. assets, according to preliminary data released by the Treasury Department on Thursday.

Japan owned $1.84 trillion of U.S. equities, long-term debt and short-term securities at the end of June 2012, the department said.

China holds $1.59 trillion.

This is the first time that Japan has held the top spot since 2008.

Japanese investors primarily boosted their holdings of fixed-income products.

The Cayman Islands, UK and Luxembourg make up the rest of the top five.

China still holds the most U.S. Treasurys, according to Treasury data for December 2012.