Oil prices fell below $US70 on profit-taking on Friday after a brief rally spurred by hopes that the worst may be over for the ailing global economy.
Early gains were also supported by continuing attacks on oil facilities in Nigeria and concerns about political developments in Iran, OPEC's second largest producer, following disputed presidential elections there.
New York's main futures contract, light sweet crude for delivery in July, shed $US1.82 from Thursday's close to end at $US69.55 a barrel after climbing past $US72.
In London trade, Brent North Sea crude for August delivery dropped $US1.87 to $US69.19 per barrel.
Traders said prices came under pressure ahead of Monday's expiry of the New York futures July contract.
Positive US data and stronger demand has driven the market in recent days, fuelled also by unrest in key oil-producing nations.
Oil prices touched multi-year lows of about $US32 in December as the economic slowdown crushed demand for energy but they have slowly clawed their way back since then.