Oil prices have slipped further in Asian trade towards six-year lows after major crude producers stressed that they will maintain output levels despite an oversupply. US benchmark West Texas Intermediate (WTI) for February delivery was down 34 cents at 45 dollars 55 cents a barrel in late morning trade, while Brent crude for February dropped 43 cents to 46 dollars 16 cents a barrel. Crude prices were already on the decline after peaking above 100 dollars a barrel in June last year. The fall accelerated end of November when the Organisation of Petroleum Exporting Countries (OPEC) decided to maintain output levels.