The biggest foreign holder of U.S. government debt had $1.19 trillion in bonds, notes and bills in August, down $33.7 billion from the prior month, the biggest drop since 2013, according to U.S. Treasury Department data released Tuesday in Washington and previous figures compiled by Bloomberg.

The portfolio of Japan, the largest holder after China, fell for the first time in three months, down $10.6 billion to $1.14 trillion. Saudi Arabia's holdings of Treasuries declined for a seventh straight month, to $93 billion.

China sold an estimated $570 billion in foreign-exchange assets from August 2015 to August 2016 in an effort to keep the currency from plunging, according to an

estimate by the U.S. Treasury released last week. It reiterated that China's efforts to support the yuan were preventing a rapid depreciation that would hurt the global economy.