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.
"There's a lot of volatility, or at least changes in direction," ABN Amro senior energy economist Hans van Cleef said. "People think the long-term trend is up, but after a gain of a few dollars, they take profit."
The dollar gained broadly against major currencies after the U.S. non-farm payrolls report showed a slowing in hiring in December but an increase in wages, setting the economy up for further interest rate increases from the Federal Reserve this year.
A stronger greenback makes oil more expensive for holders of other currencies.
Top crude exporter Saudi Arabia and fellow Gulf members Abu Dhabi and Kuwait showed signs they were cutting production in line with an agreement by OPEC and other producers, yet market watchers have doubts about overall compliance.
Saudi Arabia's state oil producer Saudi Aramco has started talks with customers globally on possible cuts of 3 percent to 7 percent in February crude loadings.
A Kuwaiti oil official said that country had also reduced production in line with the deal, and there are also reports of supply cuts from Abu Dhabi.
But there are still doubts about other producers' compliance.
"There will be some countries who will cheat...we expect zero compliance from Baghdad... And we definitely do not expect the Kurds to join in, given that they are autonomous from the federal government," Energy Aspects said in its 2017 oil market outlook, published this week.
Iraq Prime Minister Haider al-Abadi said this week the autonomous Kurdish region wasexporting more than its allocated share of oil. Iraq is the Organization of the Petroleum Exporting Countries' second-largest producer.
Iran has sold more than 13 million barrels of oil that it had long held on tankers at sea, capitalizing on an OPEC output cut deal from which it is exempted to regain market share and court new buyers, according to industry sources and data.
In the past three months, Tehran has sold almost half the oil it had held in floating storage, which had tied up many of its tankers as it struggled to offload stocks in an oversupplied global market.
National Iranian Oil Company (NIOC) is also negotiating with the Philippines over exporting four million barrels of crude per month to the country, Iran's English-language Press TV quoted a statement published on Friday by the NIOC as saying.
Iran, OPEC's third-largest oil producer, won special terms from the group's production cuts agreed on Nov. 30 and may raise output slightly.
Overall supply from OPEC in December fell only slightly to 34.18 million barrels per day (bpd) from a revised 34.38 million bpd in November, according to a Reuters survey this week based on shipping data and information from industry sources.
U.S. energy companies this week added oil rigs for a 10th week in a row, bringing the total count up to 529, the most since December 2015, energy services firm Baker Hughes said on Friday.