Hurricane Isaac was beginning to move inland on Wednesday on a slow, drenching slog toward New Orleans - seven years to the day after the much stronger Katrina hit the city.

Isaac's approach left deserted streets from New Orleans' famous French Quarter to Tampa 770 kilometers away, where Republicans at their party's national convention pressed on with only a passing mention of the storm's arrival.

The US National Hurricane Center in Miami said Isaac remained a Category 1 storm with top sustained winds of 128 km per hour, but was expected to weaken over the next 48 hours as it heads north over land. Isaac's center was forecast to pass over Louisiana for two days and head into Arkansas to the west early on Friday.