Oil prices slipped on Monday, extending last week's losses after coming under pressure over the past month from rising production in the United States, Libya and Nigeria.
The rising output has taken the edge off an OPEC-led initiative to support the market by cutting production. Signs of faltering demand have also prompted weakening sentiment, dropping prices to levels not seen since before the output cuts were first announced late last year.
U.S. West Texas Intermediate (WTI) crude futures ended Monday's session 54 cents, or 1.2 percent, lower at $44.20 per barrel, the weakest closing level since Nov. 14.
Brent crude futures were down 40 cents at $46.97 per barrel at 2:34 p.m. (1834 GMT). They posted a fourth straight weekly drop on Friday.
Prices for both benchmarks are down around 13 percent since late May, when producers led by the Organization of the Petroleum Exporting Countries extended a pledge to cut output by 1.8 million barrels per day (bpd) for an extra nine months.