The Organisation of the Petroleum Exporting Countries delivered on Thursday its most optimistic message about the global economy and the oil market since the start of the financial crisis last summer triggered a precipitous fall in prices from a record $150 a barrel to $30.

“We are beginning to see light at the end of the tunnel,” Abdalla El-Badri, Opec secretary-general, said after the cartel agreed to leave its production level unchanged, betting that the global recovery would push oil prices to $75-$80 a barrel.