* Brent, U.S. crude at lowest levels since Q3 2017
* OPEC+ to meet again if cuts not enough - UAE
* Physical markets weak as Asian refiners cut purchases (Updates prices, adds milestones)
NEW YORK, Dec 24 (Reuters) - Oil prices tumbled more than 4percent on Monday to the lowest in over a year as global stockmarkets fell on concerns about a U.S. government shutdown andworsening world economy.
U.S. crude CLc1 hit the lowest since June 26, 2017 andglobal benchmark Brent fell to the weakest since Aug. 31, 2017ahead of an early market settlement due to the Christmasholiday.
Crude futures have fallen more than 30 percent so far thisquarter, to the lowest since the third quarter of 2017, asjitters have grown about the impact of an escalating U.S.-Chinatrade dispute on global growth and crude demand.
Markets across asset classes have come under pressure as aU.S. government shutdown intensified growth concerns. Investorshave flocked to safe-haven assets such as gold and governmentdebt at the expense of crude oil and stocks.
A gauge of stocks worldwide hurtled toward an eighthstraight decline on Monday as investors ignored the U.S.Treasury secretary's actions to reinforce confidence in theeconomy and U.S. President Donald Trump criticized the FederalReserve as "the only problem our economy has."
The U.S. Senate has been unable to break an impasse overTrump's demand for more funds for a wall on the border withMexico, and a senior official said the shutdown could continueuntil Jan. 3.
Brent crude futures LCOc1 were down $2.67 a barrel at$51.15 by 1:19 p.m. ET, having touched a session low of $51.14 abarrel. U.S. crude futures CLc1 fell $2.24 to trade at $43.35,after dropping to a session low of $43.30.
Brent fell 11 percent last week and hit its lowest sinceSeptember 2017, while U.S. futures slid to their lowest sinceJuly 2017, bringing the decline in the two contracts to 35percent so far this quarter.
The macroeconomic picture and its impact on oil demandcontinue to pressure prices. Global equities .MIWD00000PUS have fallen nearly 9.5 percent so far in December, their biggestone-month slide since September 2011, when the euro zone debtcrisis was unfolding.
The U.S.-China trade dispute and the prospect of a rapidrise in U.S. interest rates have brought global stocks down fromthis year's record highs and ignited concern that oil demandwill be insufficient to soak up any excess supply.
The Organization of the Petroleum Exporting Countries andallies led by Russia agreed this month to cut oil production by1.2 million barrels per day from January.
Should that fail to balance the market, OPEC and its allieswill hold an extraordinary meeting, United Arab Emirates EnergyMinister Suhail al-Mazrouei said on Sunday.
"Oil ministers are already taking to the airwaves with a'price stability at all cost' mantra," said Stephen Innes, headof trading for Asia-Pacific at futures brokerage Oanda inSingapore. (Additional reporting by Jane Chung and Amaanda Cooper; Editingby Adrian Croft, Tom Brown and Richard Chang) ((Jessica.Resnick-Ault@thomsonreuters.com; 646-223-6052;))
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