Lower rates of production and higher consumption caused stockpiles to dip for the second week in a row.
This time a year ago, stockpiles totalled 176Mt.
The declines come as utilities are also struggling to cope with diminishing natural gas inventories.
However, storage is said to be slowly building.
Analyst Bentek estimated that US coal production fell 3% for the week to 18.4Mt, while coal consumption increased 6% to 18.3Mt.