Ecuador: Organisation of Petroleum Exporting Countries (Opec) secretary-general Abdullah Al Badri said on Friday he was not worried about reports of faster-than-expected depletion in the world's biggest oil fields.

Oil climbed toward $132 a barrel on Friday, driven by a weaker dollar and as nagging concerns about stagnating production in Russia and other countries outside the Opec group continued.

Some analysts are concerned that many of the world's biggest oil deposits are drying up and that global oil production has peaked.

Speculation

Badri repeated his position that runaway prices are caused by speculation in the marketplace and not by supply issues.

"These prices have nothing to do with shortages of oil in the market, it has to do with other factors," he said on a visit to an oil block in the Ecuadorean jungle. Mexico on Friday reported a sharp fall in output in April at its huge Cantarell offshore field which is in rapid decline.

Analysts and industry officials have predicted for decades that the world's oil output may soon plateau but oil companies downplay the "peak oil" theory.

BP data suggest the world has proven oil reserves of 1.2 trillion barrels, enough to sustain current output for 40 years.