Brent crude oil prices rose on Monday to their highest in nearly nine months after major producers said at a meeting in Vienna the global market was well on its way towards rebalancing.
The November contract was up 75 cents, or 1.3 percent, at $57.61 a barrel by 7:32 a.m. ET (1132 GMT). Brent earlier hit its highest level since January 3 and was trading within a dollar of its 2017 high of $58.37.
U.S. crude for November delivery was down 36 cents at $51.02, hitting a fresh four-month high.
"The market is OK, but these levels are beginning to look a little precarious," said Robin Bieber, technical chart analyst at London brokerage PVM Oil Associates. "The key to further upside is Brent staying over $56.65. WTI has no target higher until it can close over the 200-day at $51.01."
The Organization of the Petroleum Exporting Countries, Russia and several other producers have cut production by about 1.8 million barrels per day (bpd) since the start of 2017, helping lift oil prices by about 15 percent in the past three months.
Russia's energy minister said no decision on extending output curbs beyond the end of March was expected before January, although other ministers suggested such a decision could be taken before the end of this year.
Iran expects to maintain overall crude and condensate exports at around 2.6 million bpd for the rest of 2017, a senior official in the nation's state oil company said, while the UAE's energy minister said its compliance to supply cuts was 100 percent.
Nigeria is pumping below its agreed output cap, its oil minister said.
"On the basis of the current IEA estimates, the oil market is more or less balanced in the second half of the year," said Commerzbank in a note. "For stocks to be reduced any further, however, the oil market would have to show a deficit, so the optimism appears exaggerated."
OPEC's production cuts have been met with rising U.S. shale oil output, which has tempered the rise in U.S. oil prices relative to the increase in Brent futures.
The discount of the benchmark WTI crude contract to Brent futures has doubled in the last six weeks, as U.S. crude demand has been undermined by hurricane damage to U.S. refineries.
U.S. energy firms cut the number of oil rigs operating for a third week as a 14-month drilling recovery stalled.
Investors were also eyeing developments in North Korea. U.S. Treasury Secretary Steve Mnuchin on Sunday said President Donald Trump wants to avoid nuclear war with North Korea.
The dollar index was up 0.4 percent against a basket of currencies. The euro slipped after Germany's election showed surging support for a far-right party that left Chancellor Angela Merkel scrambling to form a governing coalition.