Brent crude for November delivery was up 1 cents at $56.87 a barrel by 0815 GMT (4.15 a.m. ET), its highest since March.
Meanwhile, Brent crude futures, the benchmark for oil prices outside the US, was down 16 cents, or about 0.3%, to $56.26 a barrel.
OPEC and 10 producers outside the cartel, including Russian Federation, first agreed late in 2016 to cap their production at around 1.8 million barrels a day lower than peak October 2016 levels, with the aim of alleviating global oversupply and boosting prices.
The market shift represents a short-term boost for North Sea oil producers after three years of low prices that have triggered steep cuts in employment in the industry's main centres around Aberdeen and forced many firms out of business.
Improving global growth, especially in emerging economies and the eurozone, is also pushing up oil prices by increasing demand for energy, while the damage to United States shale output in the wake of Tropical Storm Harvey could also lift Brent.
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Brent crude, the global benchmark, inched up 0.8% to $56.86.
Nigeria is pumping below its agreed output cap, its oil minister said.
Speaking after Friday's meeting of oil ministers in Vienna, he also said OPEC and the other producers needed to continue working closely together well into 2018. OPEC has also jumped on the opportunity to push prices higher, with the Saudis and Iraqis cutting more supplies recently than initially committed within the cartel. Crude exports from the Middle East to Asia will rise 7.5 million barrels a day between 2016 and 2040, he said.
Brent has risen by 36 percent so far in the third quarter, and is set for its strongest performance between July and September since 2004. Rather than a surge in output, there's a risk of a market squeeze emerging as early as 2018, driven by those nations because of weaker investment in exploration and development, he said. Yet even as declining rigs and inventories support the price, an extension of the OPEC-led deal beyond March will be required to rebalance the global market, according to BP Plc. All comments are subject to editorial review. Shale has been the main culprit the oil glut of the past three years, often proving a bane to OPEC attempts to push the market higher.