SINGAPORE - Oil prices fell slightly on Wednesday as investors gauged the impact of a U.S.-Iran peace deal, while uncertainty over full resumption of shipping through the Strait of Hormuz limited price declines. Both benchmarks were down about 0.2% by 0630 GMT, with Brent crude futures dipping 15 cents to $78.81 a barrel and U.S. West Texas Intermediate falling 12 cents to $75.93 a barrel.