Oil prices edged up above $99 Thursday, the first trading day after Christmas, as violence in South Sudan stoked concerns about the country's oil production.
Benchmark US oil for February delivery was up 17 cents to $99.39 a barrel in electronic trading on the New York Mercantile Exchange.
The contract inched up 31 cents to close at $99.22 on pre-Christmas Tuesday after briefly dropping below $99.
Oil prices gained nearly three per cent last week as optimism about the US economic recovery lifted expectations for the country's energy demand.
Worries over instability in South Sudan have led some analysts to predict the contract may top $100 a barrel for the first time since mid-October. On Tuesday, the UN Security Council voted to increase UN peacekeeping forces in conflict-torn South Sudan by nearly 80 per cent.
Brent crude, a benchmark for international oils, was up 11 cents at $112.01 a barrel on the ICE exchange in London.
In other energy futures trading on Nymex, wholesale gasolene rose 0.31 cent to $2.8165 a gallon, heating oil inched up 0.4 cent at $3.0725 a gallon and natural gas was up 3.1 cents to $4.447 per 1,000 cubic feet.