New York's main contract, West Texas Intermediate (WTI) for February delivery, was down ten cents at USD 100.22 in mid-morning trade while Brent North Sea crude for February gained 18 cents to USD 112.36.
US Department of Energy on Friday reported that crude inventories for the week to December 20 fell by 4.7 million barrels, more than the 2.2 million expected by analysts in a Wall Street Journal survey.
The decline was the fourth consecutive drop after a 10-week run of rises that added 35 million barrels to total stockpiles.
Desmond Chua, market analyst at CMC Markets in Sydney, said the falling inventories in the world's biggest economy underscored "stronger demand as the global outlook brightens".
The upbeat stockpiles report released on Friday, delayed due to the Christmas holidays, is supporting WTI prices above the "psychologically important" USD 100 mark, Chua said.
Investors are also continuing to monitor developments in South Sudan, where violence in a key oil-producing region has dented crude output and led to numerous oilfield staff evacuations.
More than 1,000 people have died since fighting between forces loyal to President Salva Kiir and former vice president Riek Machar broke out on December 15.
United Nations said in a statement that the number of people who have taken refuge in its bases around the country has grown to 75,000.
Analysts say the fledgling producer usually exports about 220,000 barrels of crude oil a day to Japan, Malaysia and China.


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