Crude edged higher in Asian trade today on supply concerns following escalating violence in oil-producer South Sudan. New York's main contract, West Texas Intermediate for February delivery, was up 27 cents at 99.49 dollars in mid-morning trade while Brent North Sea crude for February gained 20 cents to 112.10 dollars.Violence in South Sudan, a fledgling oil producer, escalated yesterday as its army battled rebel forces in a key oil-producing state. United Nations has double its peacekeeping force to stave off civil war. Oil production, which accounts for more than 95 per cent of South Sudan's economy, has been dented by the violence, with oil workers evacuated last week.The escalating violence has added to concerns about a disruption in global supply, following the continued curtailment of output from OPEC member Libya due to a months-long blockade of crucial terminals in the eastern part of the country.