Oil futures fell Monday after a brief rebound before the weekend, as the market focused firmly on whether OPEC is likely to cut output to tackle recent price slumps.
Brent North Sea crude for delivery in January was down 99 cents at $78.42 a barrel in London midday deals.
US benchmark West Texas Intermediate for December slid 88 cents to $74.94 a barrel.
"Oil has resumed its downward march as investors weigh up the likelihood of OPEC cutting output," said Mike van Dulken, head of research at traders Accendo Markets.
Prices sank to four-year lows last week following remarks by ministers from the Organization of Petroleum Exporting Countries (OPEC) that it is unlikely to slash output at its meeting next week.
But analysts now say the losses could push the 12-nation cartel to cobble together a deal to cut output, despite resistance from some members.
Iran, Venezuela and Ecuador have called for a cut. However, Saudi Arabia, the world's top producer and OPEC's kingpin, has reduced prices on crude exports to the US market in a move seen by some as an effort to maintain market share as it faces competition from rising shale oil production.
OPEC's next meeting is set for November 27 in Vienna, home to the cartel's headquarters.