LONDON (AFP) - Oil prices eased off their lofty summits as traders locked in profits after a record-breaking run, though analysts warned a looming strike in Nigeria could drive prices up to 60 dollars a barrel.
The price of reference light sweet crude for November delivery slipped 33 cents to 52.34 dollars a barrel in electronic trading on the New York Mercantile Exchange.
US crude oil futures spiked to 53 dollars a barrel Thursday for the first time in the contract's 21-year history, showing a gain of about six percent over the week and almost 60 percent since the start of the year.
In London Brent North Sea crude oil for delivery in November dipped five cents to 48.85 dollars a barrel in early deals.
"I just think we're seeing a little bit of profit-taking, a small retracement," said Lee Elliot, a trader with GNI-Man Financial.
"We could have a big sell-off at some stage but it's not looking likely at the moment," he added,
Traders said a strike threat in Nigeria was the latest in a long list of supply worries, with ongoing disruption to supplies from the Gulf of Mexico also a major cause for concern.
"The way things are at the moment it's conceivable that if the strike in Nigeria goes ahead you could see 60 dollars a barrel," said Simon Wardell, senior energy analyst at the World Markets Research Centre.
Investec Securities analyst Bruce Evers was even more bullish.
"US oil prices will most likely be in the 60-70 dollar price band next month," he said.
Nigerian labour unions have vowed to go ahead with a threatened nationwide general strike to protest against rising fuel prices.
"We are getting set for the strike. It is definite that it will be launched on Monday since the government has shown no intention of negotiating with us," Nigeria Labour Congress secretary general Owei Lakemfa told AFP.
Previous general strikes have done little to disrupt Nigeria's exports of around 2.6 million barrels of crude per day, but the latest action comes at a time when oil unions are already up in arms over planned job losses.
Workers at the Anglo-Dutch oil giant Shell launched a separate two-day strike on Thursday, though the company said production had not yet been affected.
Analysts said supply worries were having a magnified impact on prices because of concerns about unbridled consumption in the United States and Asia as well as the low level of commercial oil inventories.
"We kind of lose sight of the fact that this is a demand-led price run," said Wardell.
"We do have these supply worries -- we've had them all year -- but in terms of the amount of oil lost from the market because of them, it's very, very low. The underlying reason for all this is the increased demand this year."
Although prices are at record highs, adjusted for inflation they remain far below the levels reached in the wake of the 1979 Iranian revolution when prices surged to upwards of 80 dollars a barrel in today's money.