Crude slipped as Iran agreed to let Western nuclear inspectors into the country, easing concern that the conflict over its atomic energy program would disrupt Mideast supplies.

Prices fell as much as 0.8 percent after Yukiya Amano, secretary-general of the International Atomic Energy Agency, announced the accord with Iran today in Vienna. The agreement between Iran and the IAEA will be signed “quite soon,” Amano told journalists in Vienna after returning from Tehran, where the deal was reached yesterday. Negotiators are set to head to Baghdad tomorrow for a second round of talks over Iran’s nuclear program.

The Organization for Economic Cooperation and Development said Europe’s debt crisis risks spiraling and seriously damaging the world economy. Oil also fell after OECD Chief Economist Pier Carlo Padoan said “the risk is increasing of a vicious circle, involving high and rising sovereign indebtedness, weak banking systems, excessive fiscal consolidation and lower growth.”

U.S. crude inventories probably rose 1.5 million barrels last week, a Bloomberg News survey showed before an Energy Department report tomorrow. It would be the ninth week of gains. Gasoline supplies probably fell 500,000 barrels and distillate fuels, which include heating oil and diesel, also dropped 500,000, according to the survey.

Oil for June delivery slid to $91.41 a barrel on the New York Mercantile Exchange. Brent oil for July settlement gained 4 cents to $108.85 a barrel on the London-based ICE Futures Europe exchange.