Oil prices have continued to slip due to reports of an unexpected increase in US crude oil stocks and doubts over the possible extension of the current crude production cut.

Brent crude futures fell 44¢ to $63.17 a barrel, while the US West Texas Intermediate (WTI) crude futures dropped 30¢ to $57.69 per barrel, reported Reuters.

WTI prices dropped following the weekly report from the American Petroleum Institute (API), which showed an increase in US crude stocks by roughly 1.8 million barrels in the week ending 24 November to reach a rate of 457.3 million barrels.

"Brent crude futures fell 44¢ to $63.17 a barrel, while the US West Texas Intermediate (WTI) crude futures dropped 30¢ to $57.69 per barrel, reported Reuters."

WTI previously also dropped after the Keystone pipeline that supplies crude from Canada to the US resumed operations following a temporary halt.

The Organization of the Petroleum Exporting Countries (OPEC) members and various other producers are currently restricting their output by 1.8 million barrels per day (bpd) as part of an effort to boost prices.

The initial agreement is set to expire in March next year and OPEC is scheduled to meet this week to discuss future outlook.

Sources told the news agency that OPEC and key oil-curb deal participant Russia are expected to extend the deal beyond its original March expiry date, including an option to review the deal in June next year.

The reduction in oil supplies started at the beginning of this year and is seen to have reduced the oil glut.

Analysts expect that a healthy global economy is also helping the market following years of oversupply.