China, the biggest buyer of U.S. securities, trimmed its holdings for a fifth straight month.
The Treasury Department said Monday that China cut its holdings by $9.2 billion to $1.14 trillion.
Japan, the second-largest foreign holder, boosted its holdings by $17.6 billion to $907.9 billion. There had been concerns that the March 11 earthquake and tsunami would lead Japan to scale back its purchases so it could use the money for reconstruction.
Britain, the third-largest buyer, increased its holdings by 10 percent to $325.2 billion in March.
Total foreign holdings increased by $4.9 billion to $4.48 trillion.
Treasury Secretary Timothy Geithner said the government will reach its $14.3 trillion borrowing limit on Monday.
The U.S. government would default on its debt if it did not have the resources to pay bondholders the interest or principal payments as they come due. Treasury securities are considered the safest investment in the world because the U.S. government has never defaulted.
Treasury officials have said they will be able to continue regular debt auctions until August 2. That's intended to reassure domestic and foreign investors about the availabilty of Treasury securities.
Geithner on Monday said he will halt investments in two big government pension plans immediately to allow the government to continue borrowing money for the next few months. The money that the two pension funds will lose would be replaced if Congress votes to raise the borrowing limit.
Republicans have held back supporting an increase in the borrowing limit. They first want Congress agree to more spending cuts.