Oil prices retreated Tuesday after a big jump in the previous session that was fueled by speculation peace soon could reign in the Persian Gulf.

The August contract for West Texas Intermediate, the benchmark U.S. crude, fell 30 cents a barrel to $15.40 a barrel in the opening minutes of trading on the New York Mercantile Exchange.The contract had jumped 84 cents a barrel on Monday - the biggest daily increase since April - following Iran's announcement it would accept a United Nations resolution calling for an immediate cease-fire in its nearly 8-year-old war with Iraq.

Analysts said an end to the Iran-Iraq war might make it easier for the Organization of Petroleum Exporting Countries to reach agreement on limiting production in order to boost prices.