WASHINGTON -- Oil prices tumbled to a 17-month low below $56 a barrel on Friday, following a $2.50 sell-off the previous day prompted by mild autumn weather, ample winter fuel supplies and doubts about OPEC's willingness to carry out production cut.

"This is going to put pressure on OPEC to perhaps make bigger cuts," said BNP Paribas Commodity Futures broker Tom Bentz.

The Organization of Petroleum Exporting Countries, which is scheduled to meet in Nigeria next month, announced an output cut of 1.2 million barrels a day last month.

But traders have been skeptical that the Vienna-based cartel will stick to its pledge at a time of historically high prices.

Light sweet crude for December delivery declined by 45 cents on the New York Mercantile Exchange, settling and expiring at $55.81 a barrel. It was the lowest settlement for the front-month crude contract since June 15, 2005.

However, January crude futures, which become the front-month contract on Monday, climbed 40 cents to settle at $58.97 a barrel.

Analysts said the unusually wide spread between the December and January contracts signals buyers' comfort with the near-term supply fundamentals but concern about the heart of winter, when heating demand typically peaks.

If the weather remains mild, "we're looking at a supply glut," said James Cordier, president of Tampa, Fla.-based Liberty Trading.

Cordier, who views the OPEC cuts as bearish for prices because it signals weakening demand, believes Nymex crude futures are headed toward $52 this winter.

January Brent on London's ICE Futures exchange rose 45 cents to settle at $58.99 a barrel.

Many analysts remain bullish in their outlooks, citing instability in Nigeria and Iraq, a recent drop in U.S. refinery output and trading patterns that suggest the market is preparing for a late-year upswing.

Heating oil futures gained less than a penny to settle at $1.6689 a gallon on the Nymex, while gasoline futures fell 1.15 cent to settle at $1.5411 a gallon. Natural gas futures gained 8.8 cents to $7.843 per 1,000 cubic feet.