Brent crude oil prices fell to a 17-month low below $100 per barrel in volatile trade on Tuesday, a fourth straight daily decline as ample supplies weighed, while US crude rose on the expectation of dwindling fuel stockpiles.

Brent crude fell as feared cuts to supply due to violence in the Middle East have failed to materialise, and production resumed at Britain's North Sea Buzzard oilfield after a series of shutdowns and failed restarts.

In the US, expectations of another fall in crude inventories supported prices, as did news of a delayed start up of the Pony Express pipeline that will carry crude from Wyoming to Oklahoma.

Brent fell $1.04 to settle at $99.16, the lowest closing price since April 18, 2013. Earlier in the day, Brent slumped to $99.03, the lowest intraday price since May 1, 2013. On Monday, prices slid below $100 for the first time in more than 14 months.

Brent is down near 12 per cent so far this quarter, the biggest such drop since the second quarter of 2012.

US crude rose 9 cents to settle at $92.75, snapping a three-day losing streak.

"The bears are trying to run with crude, but it is a saturated trade on the short side," said Richard Ilczyszyn, chief market strategist and founder of iitrader.com LLC in Chicago. "I wouldn't be surprised to see things turn around - the low $90s for US crude is a potential buy signal."

Libya's oil output has risen to 740,000 barrels per day, the National Oil Corp said on Monday, a rise from 725,000 bpd fuelled by several oil export ports reopening.

The possibility of a cut in output by the Organization of the Petroleum Exporting Countries has kept a floor under oil prices.

Gulf Arab oil ministers hold their annual meeting on Thursday in Kuwait that could include discussions about price levels.

Top Opec exporter Saudi Arabia and other Opec members can accept oil at $100 per barrel although some delegates see lower prices as short-lived.

The market is now waiting for US crude inventory data for clues on the outlook for demand in the world's top oil consumer.

U.S. crude oil stocks likely fell 1.1 million barrels in the week to Sept. 5, according to a Reuters analysts' survey. Distillate stockpiles were forecast 600,000 barrels higher, while gasoline inventories were 200,000 barrels lower, the poll said.

The poll was released ahead of weekly inventory reports from industry group the American Petroleum Institute (API) on Tuesday and from the U.S. Department of Energy's Energy Information Administration (EIA) on Wednesday. – Reuters