Opec today kept oil supplies unchanged and began a debate about deploying production curbs in March to defend prices against a drop in demand.
The Organization of the Petroleum Exporting Countries rejected an appeal from Washington for more oil to lower fuel bills and bolster its slowing economy.
US crude by 2pm fell 87 cents to $90.86 a barrel.
Powerful Saudi Oil Minister Ali al-Naimi said he would have pushed for an output increase if it were needed but that global supply and demand were in balance.
Leading price hawks Venezuela and Iran already are suggesting Opec may need to consider output curbs at the group's March 5th meeting to put a floor under prices.
Oil inventories normally rise during the second quarter during a seasonal dip in demand and because of annual refinery maintenance programmes.
But delegates say Saudi Arabia and its Gulf allies would prefer to see prices down from $90 to ease recessionary pressures that will dampen demand for Opec's oil.