Oil prices fell below $81 a barrel Monday in Asia amid investor concerns flagging U.S. crude demand doesn't justify the recent rally.

Benchmark crude for April delivery was down 40 cents to $80.84 a barrel at midday Singapore time in electronic trading on the New York Mercantile Exchange. The contract rose 60 cents to settle at $82.09 on Friday.

Oil prices jumped from $69 early last month on expectations an improving U.S. economy would bring crude demand up with it. But oil consumption has lagged, and prices have stalled in the low $80s for the last week.

"U.S. demand for oil is falling," energy consultant Stephen Schork said in a report. "Until we see a decrease in unemployment and an increase in consumer confidence we will remain on guard for a double dip recession."

Investors will be eyeing this week's Federal Reserve meeting for signs of when policymakers may start raising record-low interest rates.

In other Nymex trading in April contracts, heating oil was down 0.2 cent at $2.092 a gallon, and gasoline dropped 0.4 cent to $2.251 a gallon. Natural gas declined 4.3 cents to $4.357 per 1,000 cubic feet.

In London, Brent crude was down 40 cents at $78.99 on the ICE futures exchange.