Updated from 2:37 p.m. EDT

Oil prices fell Monday after finally closing above the $55-a-barrel level for the first time ever last Friday.

The December futures contract closed down 63 cents at $54.54 a barrel in regular floor trading on the Nymex, after gaining in premarket trading. Prices remain about a dollar below the record intraday high of $55.43 touched two weeks ago.

Unusually strong global demand amid periodic supply disruptions has taken the benchmark U.S. crude to new highs on almost a daily basis in the past five weeks.

It is the latest leg in a yearlong rally that has driven prices up about 75%.

Traders' most recent concern is short supplies of heating oil ahead of the winter season.