Crude oil slipped further following a slide conditioned by the rise in inventories, confirmed both by the Energy Department and the American Petroleum Institute.

The data are a "big plus for consumers -- inventories rise and [are] confirmed in tandem by both agencies, which is a shock as they have been at odds in recent weeks," said John Person, president of National Futures Advisory Services.

Now crude oil is trading at $43.88.

According to the Energy Department, cruse supplies reached 295.9 million barrels in the week ended Dec.17, rising 2.1 million barrels.

The API sets the inventory level at over 300 million barrels, a 2.9 million barrels increase for the week.

"Ample crude stocks will assuage market concerns that supplies may be inadequate to meet strong demand during the winter heating season," said Thorsten Fischer, a senior analyst at Economy.com.

Oil prices relief was thwarted by the surge of violence in Iraq where 22 or more people were killed in Mosul on Tuesday.

“With the extremely deadly action unfolding in Iraq and the market somewhat concerned about an all-out last ditch insurgent effort up to and into the January elections, violence will continue and that upgrades the risk against Iraqi oil facilities," said John Kilduff, an analyst at Fimat USA.