Oil prices fell to a one-year low on Tuesday, deepening a rout that has plunged the energy complex into a bear market as growing supply is poised to swamp demand next year.

The latest drop came after President Donald Trump urged OPEC and Saudi Arabia to maintain their current policy of gradually increasing output, which helps to cap oil prices. OPEC and its oil allies are mulling a fresh round of production cuts following a collapse in prices over the last six weeks.

The group could announce the new output curbs at a meeting next month, but Trump's intervention injects uncertainty into the alliance's decision-making.

U.S. West Texas Intermediate crude ended Tuesday's session down $4.24, or 7.1 percent, at $55.69, its lowest closing price since Nov. 16, 2017. Tuesday's decline extended WTI's record losing streak into a 12th consecutive session.

Brent crude fell $4.28 a barrel, or 6.1 percent, to $65.84 by 2:25 p.m. ET, after tumbling to its lowest level since March.

Both WTI and Brent have fallen more than 20 percent from their four-year highs last month, putting them in bear market territory.

The pullback began in October when crude futures fell in tandem with stocks during a broad market sell-off that saw investors shed risky assets. Signs of looming oversupply in the market have put additional pressure on oil prices.

The world's appetite for oil is still expected to surpass more than 100 million barrels per day next year, but forecasters have steadily revised their projections for demand growth lower. Even as the demand outlook weakens, OPEC and Russia have been hiking output and supplies are surging from the United States.

On Tuesday, OPEC knocked down its forecast for 2019 demand growth for the fourth time in as many months. The cartel said production increases from non-OPEC countries will outpace demand growth next year.

"The recent downward revision to the global economic growth forecast and associated uncertainties confirms the emerging pressure on oil demand observed in recent months," OPEC said.