On Sunday, Abdalla el-Badri, Secretary General of the Organization of Petroleum Exporting Countries, warned that oil prices of $50 per barrel are “insufficient for continued investment” and urged a $70 barrel.

Algerian Energy Minister Chakib Khelil predicted on Sunday that prices would rise to $60 a barrel by the end of this year.

“For high-cost projects, you probably do need a higher price level to be economically viable,” said Ben Westmore, an energy analyst with National Australia Bank in Melbourne. “Once activity in the global economy comes back, we could see supply constraints leading to higher prices.”

“People are starting to think longer term about the supply side,” Westmore said.

But Kuwaiti Oil Minister Sheik Ahmed Al Abdullah Al Sabah said Sunday that a price of around $50 a barrel is “reasonable” for crude considering the global economic slowdown. He said OPEC should wait for the results of massive stimulus packages by governments around the world before deciding whether to cut production at the cartel’s next meeting on May 28.

OPEC has announced output quota reductions of 4.2 million barrels a day since September.

In other Nymex trading, gasoline for May delivery fell 1.70 cents to $1.43 a gallon and heating oil slid 2.13 cents to $1.35 a gallon. Natural gas for May delivery dropped 5.6 cents to $3.24 per 1,000 cubic feet.