Oil fell below $50 a barrel on Monday, under pressure of uncertainty associated with the possible extension of OPEC's cuts.
OPEC members and other producers agreed on Sunday to reconsider their views regarding the deal extension to reduce the extraction of raw materials.
Brent crude fell 19 cents at $50.61 after U.S. crude fell 31 cents at $47.66.
"There are troubling times for oil bulls," said Stephen Brennok from brokerage PVM Oil Associates Ltd in London.
OPEC members and other oil producers met in Kuwait to review the progress of their cuts that began in January and will last until the end of June.
Although many OPEC members expressed support for the extension of the reductions, Russia's position in this matter was less certain. Energy Minister Alexander Novak said on Sunday that it was too early to say whether renewal.
"The market has a "growing skepticism" about the chances of an agreement extending the production of oil," - analysts at JBC Energy said in a report.
Oil also came under pressure from the additional evidence that the higher prices as a result of the OPEC cuts are helping to increase the supplies in the U.S.
U.S. increases the number of oil rigs for a 10th consecutive week.
Despite the availability of adequate inventory and growth made in the U.S., Goldman Sachs said that the market was rebalanced, but it does not help in oil cuts.