ABU DHABI (AFP) - Opec cannot protect world oil prices which have plunged since June, the United Arab Emirates said on Tuesday, arguing that rising North American shale oil output needed to be curbed.

"We cannot continue to be protecting a certain price," UAE Energy Minister Suhail al-Mazrouei said.

"We have seen the oversupply, coming primarily from shale oil, and that needed to be corrected," he told participants in the Gulf Intelligence UAE Energy Forum in Abu Dhabi.

Oil prices continued their slide towards six-year lows in Asian trade on Tuesday. Brent crude for February delivery fell 75 cents to US$46.68 a barrel - its lowest level since April 2009. On Monday, it plunged more than 5 per cent to end below US$50.