Oil widened losses in American trade, marking second gains in row and giving up 2019 highs on active profit-taking on concerns of global growth slowdown.
As of 13:15 GMT, US crude fell $56.05 a barrel, while Brent retreated to $65.95.
US crude slipped 0.1% yesterday, the first loss in six days, while Brent declined 0.1% as well off three-month highs.
Oil prices are retreating on profit-taking amid caution on lower global demand due to slower growth.
US production continues at record highs, in turn hurting efforts by OPEC and Russia to support the market.
US output rose by 2 million bpd in 2018, a 20% surge, while up 40% from mid-2016 levels.