By Eric Yep 

Crude-oil futures were lower in European trade on Monday as investors weighed supply-demand fundamentals amid weakening confidence in the latest price rally.

On the New York Mercantile Exchange, light, sweet crude futures for delivery in June traded at $56.77 a barrel at 1004 GMT, down $0.4. June Brent crude on London's ICE Futures exchange fell $0.4 to $64.88 a barrel.

Nymex West Texas Intermediate crude lost a marginal 0.3% last week, snapping a five-week winning streak, while Brent crude gained 2.9% last week and has been up for three consecutive weeks, rising by 18.8%.

While Brent crude has been supported by Saudi Arabia's military action in Yemen, U.S. oil prices have been under some pressure lately after weekly stockpiles rose despite expectations that U.S. oil production may begin slowing soon.

But oil is still trading near its highest level seen this year.

"Sustaining the recent oil price rally requires firmer demand and a tangible supply response. The cart is moving ahead of the horse, and we take a cautious view on further price appreciation over the near term," Barclays analyst Michael Cohen said in a report.

He said there is little evidence to suggest that a broad pickup in consumption is occurring, while on the supply side agency forecasts released in the past month show shale growth could materialize again if oil prices stay in the $60-$70 price range.

Bank of America Merrill Lynch said it sees WTI prices returning to $50 a barrel as refinery maintenance kicks in again in September. After that, it sees a recovery to $57 a barrel by year-end.

"Initially, the oil market surplus was reflected in large increases in crude inventories, placing downward pressure on crude oil prices, timespreads and differentials," the bank's analysts wrote. "Now we are about to see petroleum products building as refineries ramp up after maintenance."

A few other indicators also signal that the current crude-price rally may be running out of gas.

Exchange-traded funds that invest in U.S. oil futures, including the $3.1 billion United States Oil Fund LP, have registered about $2.7 billion of investor outflows this month, according to investment bank Macquarie Group Ltd. These ETFs took in roughly $6 billion this year through mid-March, when the U.S. oil benchmark hit a six-year low.

Meanwhile, striking workers have shut down an important Libyan oil field in a dispute over wage payments, a Libyan official said Sunday. The field is jointly run by Italian energy giant Eni SpA and Libya's National Oil Co.

Later this week, financial markets will be focused on the U.S. Federal Open Market Committee meeting on Wednesday.

Nymex reformulated gasoline blendstock for May--the benchmark gasoline contract-was flat at $1.9918 a gallon. ICE gasoil for May changed hands at $585.00 a metric ton, down $2.25 from Friday's settlement.

Summer Said contributed to this article

Write to Eric Yep at eric.yep@wsj.com

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