NEW YORK, Dec 4 (Reuters) - A single bank sold a large

volume of U.S. oil futures contracts in early afternoon trading

on Wednesday, a person with direct knowledge of the matter said,

pushing prices down more than 1% within minutes and causing

traders to scramble to decipher the reason.

The sale, just hours ahead of an OPEC+ virtual meeting at

which the group is expected to extend supply cuts through the

end of the first quarter, left traders scrambling to make sense

of the rationale for the transaction.

The bank sold 4,000 lots of U.S. West Texas Intermediate

crude oil futures in a single block at $69.21 a barrel

around 1 p.m. EST (1800 GMT), the person said. The buyer then

sold the contracts immediately afterwards, putting pressure on

prices, they added.

A spokesperson for CME Group ( CME ), owner and operator of

the New York Mercantile Exchange on which WTI futures are

traded, confirmed that an outright block of that size traded.

They declined to disclose the identity of the parties involved.

WTI futures for January delivery fell from $69.42 a barrel

at 12:59 p.m. to $68.76 a barrel by 1:00 p.m.

WTI futures settled at $68.54 per barrel, down $1.40, or 2%.

A lot of WTI futures equates to 1,000 barrels of oil,

putting the value of the 4,000-lot trade north of $270 million.

The average volume for the front-month WTI contract on the

New York Mercantile Exchange since Sept. 4 has been around 200

lots per minute, according to data from financial firm LSEG.

"Everyone's trying to figure this out," Mizuho analyst

Robert Yawger said when asked about the sharp sell-off. "I have

not seen any headlines that would explain it."