The Organisation of the Petroleum Exporting Countries (Opec) Secretary-General said on Sunday Opec and non-OPEC producers should work together to stabilise oil markets, suggesting oversupply could amount to two million barrels per day (bpd).

But Abdullah al-Badri added in remarks to a conference in Bahrain he had no doubt markets would return to balance in the second half of 2015, explaining that he did not believe fundamentals warranted a price drop of the extent markets had seen.

"Tremendous opportunity" in oil remained, despite recent market volatility and uncertainties, he said, adding that the industry's long term outlook remained healthy.

Oil prices have slid sharply in recent months as a result of a large supply glut, due mostly to a sharp rise in US shale production as well as weaker global demand.

The rapid decline has left several smaller oil producing countries reeling and has forced oil companies to slash budgets.

Yet Badri said he expected energy demand to increase by 60 per cent by 2040 and oil would remain a central energy source.

Badri said that since 2008, supplies from non-Opec producers had risen by almost six million bpd, while in contrast Opec production had been fairly steady at about 30 million bpd.

Meanwhile, United Arab Emirates oil minister Suhail bin Mohammed Al-Mazroui said the market will decide a fair and sustainable price for oil. -Reuters