China's holdings of US Treasury bonds in September hit their lowest in a year, but the country remained the largest foreign buyer of US government debt, statistics released Friday by US Department of the Treasury showed.

China's holdings of US Treasuries totaled 1.151 trillion US dollars in September, down by 13.7 billion US dollars from the previous month.

The statistics also showed that Japan, the second largest foreign buyer, is a net seller of US Treasuries in September, too, with its holdings slipping from 1.03 trillion US dollars to a one-year low of 1.028 US trillion dollars.

The data represented an aggregation of purchases and sales by both foreign official institutions and private investors. Together, US Treasuries saw a net foreign outflow of 29.1 billion US dollars in September.

Of that, net foreign private inflows were 23.5 billion US dollars and net foreign official outflows were 52.7 billion US dollars, meaning that the foreign private sector remained a net buyer while foreign official institutions contributed more to the selling activity.

Washington has increased the issuance of its government bonds since the massive corporate tax cut was enacted last December. Business insiders have warned of imbalance between demand and supply.

"I think we have a supply-demand problem for bonds that will particularly come next year or the year after," said Ray Dalio, founder of the world's largest hedge fund company Bridgewater Associates.

"In other words, because of that tax cut and the deficit, we'll have to sell a lot more bonds, and the United States itself can't absorb that quantity of bonds," he told CNBC in an interview on Thursday.