Brent prices maintained their losses in American trade on track for the first loss in five days, nearing eight-month lows anew on concerns of lower global demand as growth forecasts recede.
As of 13:10 GMT, Brent declined to $66.00 a barrel, with a session-high at $66.84, and a low at $65.83.
Brent rose 0.1% on Monday, the fourth profit in a row away from eight-month lows at $64.63.
Concerns are mounting over global demand as growth slows down in Europe and China, while emerging economies continue to suffer.
The International Energy Agency warned OPEC and allies of the negative impact of cutting supplies yet again on concerns over higher prices, which would harm consumption.
OPEC, led by Saudi Arabia, and Russia are reportedly seeking to cut output by a million to 1.4 million bpd to buoy prices and avoid another supply glut.