Crude oil prices weakened on Friday after data showed US production had picked up.
Data from the Energy Information Administration (EIA) showed US oil output had risen to 9.75 million barrels per day as at January 12, versus 9.49 million barrels at the beginning of 2018.
Brent crude oil futures traded 1% lower as at 0730 GMT, at $68.62 per barrel.
US crude production is expected to continue rising in the weeks ahead, breaching the 10 million barrels per day mark, a factor that could lead to further near-term weakness.
On Wednesday, a monthly report from OPEC also highlighted the trend of higher North American production, pointing out that improved technology had helped producers in the region lower their breakeven costs.
With oil prices having risen considerably over recent months, from $52 per barrel at the beginning of September, there is plenty of incentive for such producers to raise output further.
“The upside is now limited for oil prices. US oil producers will ramp up production in the coming months,” said Fawad Razaqzada, a market analyst at Forex.com.
On the upside, however, talk of possible attacks on Nigerian oil assets from militant group Niger Delta Avengers has provided some support for the market this week.
Analysts said a major attack on Nigeria´s oil production could have important repercussions for the global market given the country´s status as Africa´s biggest producer.