Benchmark crude oil futures dropped amid speculation a slowing Chinese economy would hit fuel demand in the country, the world's second-largest oil consumer.
The March West Texas Intermediate contract lost about 94 cents to $93.65 a barrel on the New York Mercantile Exchange and hovered at $94.41 at 9:01GMT.
The February WTI contract, which expires on 21 January, shed 20 cents at $94.17. It gained 41 cents to $94.37 on 17 January, the highest finish since 2 January. The volume of all contracts traded was more than four times the 100-day average.
Elsewhere, the March Brent contract shed some 7 cents to $106.28 a barrel on London's ICE Futures Europe exchange. The European benchmark crude was at a $12.54 premium to WTI, as against $11.89 on 17 January.
Purchasing Managers Index (PMI) data from China, due out on 23 January, is expected to show that factory activity in the world's second-largest economy slid in January.
The HSBC and Markit Economics gauge of manufacturing probably fell to 50.3 in January from 50.5 in December, according to a Bloomberg poll of 17 economists.
Meanwhile, the US Energy Department is expected to put out supply data on 23 January.
Transactions would be booked on 21 January for settlement purposes, as the US markets were shut on 20 January for the Martin Luther King Jr. holiday.
"We're looking ahead to inventory data and PMI from China to get a guide," Michael McCarthy, a chief strategist at CMC Markets in Sydney told the news agency. He predicts investors may buy WTI contracts at about $92 a barrel.
"We got very little lead from the US overnight, and European trading was muted," McCarthy added.
UniCredit Research said in a 20 January note to clients: "The most recent data show that crude stockpiles in the US declined more than expected. Since the end of October, the stockpiles have declined by roughly 35mn barrels, compared to an average decline of only 20mn barrels for the same period in the last five years. Nevertheless, the spike in the [Brent crude] oil price that this news could conceivably have triggered failed to materialise, since its impact was offset by hopes of an improvement on the supply side."
"These were based first on Libya, where oil production has improved, although it remains unstable. Second, the EU is set to lift the ban on reinsurance for tankers transporting Iranian oil to India, China, Japan, South Korea, Turkey and Taiwan for the coming six months. This ban was part of a package of sanctions, some of which are to be lifted according to an interim agreement reached between Iran and the West in November 2013, following an announcement today by the International Atomic Energy Agency that Iran has halted and in some cases scaled back the development of its nuclear program."
"However, the lifting of the ban is likely to bring only a slight improvement in the supply situation, since the import ban in the EU remains in effect. In contrast, a major impact [on Brent crude] would be expected if a long-term accord were reached that led Europe to ease its current import restrictions," the Italian firm added.
In China, factory production increased 9.7% in December, the slowest pace since July, government data showed on 20 January.
WTI gained 1.8% in the week ended 18 January. US crude drew support from a weekly-report by the US Energy Information Administration (EIA) that revealed a larger-than-expected draw of 7.7 million barrels last week, bringing the seven-week decline in inventory to 41.2 million barrels.