Crude oil rose slightly in Asian trade on Wednesday, as investors stayed on the sidelines ahead of a closely watched inventory report on US energy supplies. New York's main contract, light sweet crude for delivery in September gained 5 cents, to 77.63 dollars a barrel.London's Brent North Sea crude for September rose 9 cents, to 76.31 dollars a barrel.Investors were also watching a tropical system brewing near the Caribbean island of Hispaniola, which could head towards the Gulf of Mexico, home to roughly 30 percent of US petroleum production.