A strengthening Tropical Storm Isaac is likely to hit the US Gulf Coast with hurricane force, forecasters say.
After lashing southern Florida, Isaac is heading towards the northern Gulf Coast, threatening New Orleans seven years after Hurricane Katrina hit.
Louisiana, Florida, Mississippi and Alabama have declared emergencies.
The Republican Party has delayed the start of its national convention in Tampa, which is to formally nominate Mitt Romney for president, by a day.
But concerns about severe weather remain, with organisers keeping a nervous eye on Isaacs progress north-west.
The Republican governors of Alabama and Louisiana have cancelled their trips to the convention to focus on disaster prevention efforts. (BBC)
