New York's main oil futures contract, light sweet crude for July delivery, dropped 77 cents to $134.09 per barrel, as the European trading day began.
Brent North Sea crude for August delivery lost 86 cents to $134.25.
UN Secretary General Ban Ki-moon, after a weekend visit to Saudi Arabia, said Saudi Oil Minister Ali al-Nuaimi told his kingdom would raise production by 200,000 barrels a day in July on top of a hike of 300,000 barrels made in June.
"They will respond positively whenever there is a request from their customers, so there is no shortage," Ban said. He said that "they don't want to be blamed" for high oil prices.
The price of New York crude hit a historic high point of almost 140 dollars a barrel earlier in June as oil consumers fretted over a feared tight supply situation amid robust demand for energy.
Oil prices broke through 100 dollars for the first time ever only at the start of 2008 and began 2007 trading at about $50.
Global finance officials fear high oil prices pose a threat to world economic growth, while truckers and others in Europe and Asia are holding protests over the rising cost of fuel.