The euro slipped on Wednesday after news of a surprise drop in German industrial orders, while the dollar was futher boosted by its safe-haven status amid downbeat US data.
A stronger greenback makes dollar-priced crude more expensive for buyers using weaker currencies. In turn, that tends to weigh on oil demand and prices.
Traders were meanwhile awaiting the US Department of Energy's weekly oil report, which will be published on Thursday, one day later than normal, because of a public holiday on Monday.
"Due to a lack of the economic indicators, investors will be keeping an eye on the US dollar movements and the direction of the global equity markets for further signs of the economic conditions," added Sokou.
European stock markets fell on Wednesday as many traders cashed in the previous day's gains and fretted over the prospects of economic recovery in Europe and the United States.
Oil prices sank for the seventh session running on Tuesday after a steeper-than-expected slowdown in the US Institute for Supply Management's non-manufacturing index.
The index declined to 53.8 points last month from 55.4 in May. Most economists had expected the June figure to be 55.0.
"Oil markets continued on the downward trajectory seen for the duration of last week and earlier this week," said analysts at energy consultancy John Hall Associates.
"Ongoing weak economic signals continue to impact market sentiment, with the surplus of supply over demand showing few signs of dissipating."
