Oil climbed on Friday, approaching its highest level since the summer of 2015 a day after OPEC and other major producers agreed to continue reining in output until the end of 2018 to try to reduce the global oil glut and boost prices.
The Organization of the Petroleum Exporting Countries and some non-OPEC producers led by Russia agreed on Thursday to keep current limits on output in place until the end of next year, although they signaled a possible early exit from the deal should the market overheat and prices rise too far.
U.S. light crude ended Friday's session 96 cents, or 1.7 percent, higher at $58.36, but finished the week 1 percent lower.
Brent was trading at $63.67, up $1.04, or 1.7 percent on the day. For the week, the contract was down nearly half a percent.
Oil prices pared gains as the broader market sold-off in the wake of a report that former U.S. National Security Adviser Michael Flynn will testify that President Donald Trump directed him to hold talks with Russians.
In November, both oil benchmarks traded at their highest levels since June 2015 with Brent hitting $64.65 and WTI at $59.05. They respectively gained 3.5 percent and 5.5 percent in the month.
"The market is giving the OPEC, non-OPEC accord its due. The Saudi oil minister came across as resolute and determined to see global crude oil inventories reduce," said John Kilduff, partner at energy hedge fund Again Capital LLC in New York.
The deal, which has been in place since January and was due to expire in March, has seen producers reduce output by 1.8 million barrels per day (bpd), helping to halve global oil oversupply over the past year.
It has allowed prices to return above $60 per barrel, recovering from lows of $27 per barrel hit in January 2016. But the price rise has also revived the specter of the bull market of the last decade when Brent prices soared.
These concerns led Russia to stress the need for clarity on an exit strategy from the deal and to this end, a reference to a review process in June was included.
Saudi Oil Minister Khalid al-Falih said it was premature to talk about exiting the cuts for at least a couple of quarters, as the world was entering a season of low winter demand.
"It leaves a question mark about the second half of 2018 and about the commitment of Russian oil companies, which will be price dependent," Petromatrix strategist Olivier Jakob said.
The CEO of Russia's top private producer Lukoil told Reuters that should the oil market overheat, both OPEC and its allies will release new production to rebalance it. The oil market is unlikely to overheat, he added, thanks to cooperation between OPEC and its allies which would allow them to release new output.
Price rises could also fuel more drilling in the United States, which is not party to the agreement, Russia warned.
Rising U.S. production has been a thorn in OPEC's side, undermining the impact of its output curbs. U.S. oil production hit a new record of 9.68 million bpd last week, according to government data released this week.
U.S. energy companies added two oil rigs in the week to Dec. 1, bringing the total count up to 749, the highest since September, General Electric Co's Baker Hughes energy services firm said in its closely followed report on Friday.
"Countries involved in the (OPEC) deal ... will keep a close eye on U.S. oil production and will not shy away from taking appropriate steps to counter its impact, said Abhishek Kumar, Senior Energy Analyst at Interfax Energys Global Gas Analytics in London.
— CNBC's Tom DiChristopher contributed to this report.