Oil traded higher on Friday as investors bought futures ahead of the weekend, but a strong U.S. dollar limited gains, as did lingering doubts about whether all OPEC producers would cut output in line with an agreement.
Trading was choppy, and market players cited end-of-week position-squaring and relatively low volumes during the first trading week of the year.
Brent crude futures, the benchmark for international oil prices, were up 11 cents at $57 per barrel at 2:35 p.m. ET (1935 GMT), having swung from a high of $57.47 to a low of $56.28.
In the United States, West Texas Intermediate (WTI) crude futures settled up 23 cents at $53.99 a barrel, recovering from a session low of $53.32 and off a high of $54.32.
The contract rose about 0.5 percent on the week, marking the fourth straight weekly gain.