US crude fell 28 cents to $70.75 a barrel by 1139 GMT, and Brent crude fell 33 cents to $70.52 a barrel.
"Recently, the oil market is looking more at the correlation between the euro and the dollar," Ryuichi Sato, an analyst at Tokyo-based Mizuho Corporate Bank told Reuters.
The dollar firmed against the euro as European shares turned lower. The US unit initially slipped close to $1.40 against the single currency.
The fifth straight day of drops in European equities also weighed on prices, with concerns over the fragility of any economic recovery prevalent across markets.
Oil prices have been trading in a tight range around $70 a barrel over the past week, as investors assess whether the rally which has seen prices more than double since February will continue.
Oil prices had initially inched higher today after Chinese oil data showed diesel exports fell to 390,000 tonnes in May from 510,000 tonnes in April, as oil firms kept more fuel at home on rising demand and falling stockpiles.
The Chinese customs data came as the World Bank raised its forecast for gross domestic product growth this year for the world's third-largest economy to 7.2% from the 6.5% projected in its previous quarterly report in March.
The World Bank said a massive policy stimulus should enable China to keep growing at a respectable rate this year and the next, but a robust recovery was unlikely given global weakness and softness in non-government investment.
Growing demand for oil from emerging economies like China and India was one of the main reasons prices spiked to record highs near $150 a barrel last year, before the economic crisis crimped consumption across the globe.
"Demand is certainly lower than last year but there are tentative signs of improvement," analyst Andrey Kryuchenkov at VTB Capital in London said.
Falling crude inventories and an uptick in gasoline demand in the US also supported prices, but enough concerns remain about the strength of global demand during the recession to leave prices vulnerable to a correction, analysts said.
The US Energy Information Administration (EIA) reported a much higher than expected fall in crude stockpiles in the week to 12 June, by 3.9 million barrels.
Gasoline demand in the world's top consumer rose over the last four weeks according to the EIA, boosted by lower prices at the pumps compared with last year.
But demand for oil products as a whole was still down 6 percent on last year as the recession has slashed demand for more industrial fuels like diesel, heating oil and jet fuel.
