Beijing, which has converted much of a huge trade surplus with the United States over the past two decades into buying up US treasuries and other securities, held 26.1 percent of the total of $4.44 trillion held by foreigners, the Treasury said.
The figures came as the US government recalculated its data on foreign holdings of US securities from June 2010.
Chinese-held Treasuries have fallen since hitting a high of $1.18 trillion in October, under the revised figures. Japan remained by far the second largest holder of US government debt, with $882 billion in December, around $1.3 billion less than original estimates.
Britain was third at $272.1 billion.