New York's main contract, light sweet crude for delivery in January, slid 24 cents to $89.14 a barrel in the afternoon.
Brent North Sea crude for January delivery fell 43 cents to $91.02.
"The whole market is reacting on the downside because the Chinese central bank may be raising interest rates this weekend," said Serene Lim, oil and gas analyst for ANZ bank in Singapore.
"That's weighing the markets because any raise in the interest rates... would lead to slower economic growth and oil demand growth," Lim added.
The official China Securities Journal Tuesday quoted unnamed analysts as saying the probability of an interest rate hike in the world's biggest energy consumer in the near term was "very great".
The paper also said the days before and immediately after this weekend were a "sensitive window" for rate hikes, with China releasing its consumer price index (CPI) for November on Monday.
Analysts widely expect November's CPI to remain elevated after figures released last month showed October's index hitting a two-year high.
"The continued rise of the CPI has increased the pressure for an interest rate hike," the China Securities Journal reported.
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