WASHINGTON - China, the biggest buyer of US Treasury securities, trimmed its holdings for a fourth straight month in February and Japan boosted its holdings one month before a devastating earthquake hit the country.

US?Treasury Department says China reduced its holdings by $600 million to $1.15 trillion. Japan, the second largest foreign holder, boosted its holdings by $4.4 billion to $890.3 billion.

There have been concerns that the March earthquake and tsunami may cause Japan to scale back its purchases in order to use the money for reconstruction.

Total foreign holdings increased 0.5 percent to $4.47 trillion. However, as US government moves closer to the $14.3 trillion debt limit, it will have to scale back sales unless Congress moves to raise the limit.