It peaked above $86 a barrel in early October, a four-year high.
Meanwhile, prices have fallen at the pumps, from an average of over $2.80 last month to just under $2.60 on Friday. None of that is bullish for oil, which powers the world economy.
An OPEC official added that the cut "would be more discreet", would "be a quid-pro-quo" between the Saudis and Trump, and also avoid a confrontation with non-OPEC member Russian Federation, which is reluctant to enact any cutbacks.
Activity in Germany - Europe's largest economy - and France also lagged.
However, some energy investors have expressed concern the decreasing oil prices could trigger a new bust in United States production. At the same time, Opec said demand is likely to fall. Although the Organization of the Petroleum Exporting Countries is expected to curb output, rising USA oil supply has fueled persistent concerns about a global surplus.
European Union Leaders Approve Brexit Plan
May herself repeated this, telling reporters in Brussels: "This is the best possible deal, it's the only possible deal". Nothing better sums up the 26-page declaration on post-Brexit relations: it promises everything and nothing.
Still, Friday's drop in prices reflects market concern that OPEC production cuts are "not going to be enough to support prices", Lipow added.
It was also thought that USA sanctions on Iran could stop it exporting to major customers, holding back supply, but most of the country's key clients have been allowed to maintain their access.
But this has done little so far to prop up prices.
Iran's exports have dropped by several hundred thousand barrels per day (bpd) this month, a leading tanker-tracking company said on Thursday, suggesting USA sanctions that kicked in this month have scared off many buyers. Against that backdrop, the slowing pace of Chinese growth, and therefore energy demand growth, is a concern.
But as NPR's John Ydstie reports, falling oil prices could have negative effects in the longer term as a result of oil's increasingly large share in the US economy.
Turkey's Foreign Minister Accuses Trump Of Turning 'Blind Eye' To Khashoggi's Murder
Washington Post columnist Jamal Khashoggi was killed on October 2 while visiting the Saudi Consulate in Ankara, Turkey. For its part, Saudi Arabia has said that 21 people are in custody, with death penalties sought against five men.
JP Morgan has slashed its Brent Crude forecast for 2019, due to expected surge in supply from North America in the second half of next year, Scott Darling, head of Asia-Pacific oil and gas at JP Morgan, told CNBC on Thursday.
OPEC is now expected to implement new supply cuts after its upcoming meeting on 6 December.
"The increased tensions between the USA and China are adding to the intensely sour sentiment in energy markets", TD Securities analysts led by Bart Melek wrote in a note to clients Friday. Those factors pushed up oil's volatility this week to the highest since early 2016.
If OPEC decides to cut production at its meeting next month, oil prices could recover, analysts say.
Trump's opposition to higher oil prices is particularly important because he has so far refused to take action against Saudi Arabia over the murder of journalist Jamal Khashoggi.
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A vote on the motion to speed the legislation through the Commons could come as early as Friday. Meanwhile, the federal government is trying to push a back-to-work bill through the Commons.
Apart from the obvious fact that the news agency let the cat out of the bag and the scheme is now doomed to failure, the analytical line of thinking assumes that OPEC is free and clear to decide however it wants to enact the cutback, when in fact members including Iraq, Libya, and Nigeria side with Russian Federation in that they intend to boost production in 2019, not reduce - and this could cause a rocky G2 summit and Vienna meeting. "So, for all we know, January demand from Saudi Arabia will be even lower". "How much longer (are) bears are able to keep firing?"