Oil eased to around $71 a barrel on Monday after climbing to a 10-month high last week on concern about low fuel supplies in top fuel consumer the United States.
Threats to oil supplies in Nigeria, the world's eighth-largest oil exporter, were likely to limit the decline in prices, analysts said. A general strike is due to start in Nigeria on Wednesday.
There's a lot of very constructive factors out there and I think they're all priced in at the moment, said Mike Wittner of investment bank Calyon. But there's really no bearish factors to pull the market down.
London Brent crude for August, seen as more representative of global prices, fell 25 cents to $71.22 a barrel by 1309 GMT. U.S. crude for July slipped 19 cents to $67.81.
Brent hit a 10-month high of $71.88 on Friday after the latest report on U.S. fuel stocks showed gasoline stockpiles failed to rise and refinery use declined, adding to concern about summer fuel supply.
Oil has climbed from around $50 in January towards the all-time highs close to $80 reached last year and analysts say the bull run may have some way to go yet.
Societe Generale said in a report that $70 a barrel should now become the new short-term floor for Brent. The bank also said crude has potential to reach $75 in July.
In Nigeria, gunmen overran an oilfield station on Sunday and Italian oil company Eni said 27 people were being held hostage at the facility, which normally produces about 40,000 barrels per day of oil.
About 600,000 bpd of the country's output is shut down because of militant attacks. Nigerian unions will start a general strike on Wednesday, the umbrella union body said on Monday.
The supply risks come as world oil demand is growing faster than expected, according to the International Energy Agency, an adviser to 26 industrialised countries.
Last week, the IEA raised its forecast for world oil demand this year and called on the Organization of the Petroleum Exporting Countries to increase output. OPEC insists crude supply is sufficient.
U.S. crude hit a record $78.40 nearly a year ago on fears that fighting between Israel and Lebanese Hizbollah guerrillas could spread to Middle East oil producers.
Iran's chief nuclear negotiator and the European Union's foreign policy chief may meet again in the next few days for talks on Iran's atomic programme, an issue that has underpinned prices this year.