Tropical storm Edouard triggered a hurricane watch by US weather officials early Monday as it churned westward toward Louisiana and Texas on the US Gulf coast.

The National Hurricane Center in Miami, Florida, issued a tropical storm warning for Edouard westward from the mouth of the Mississippi River, near New Orleans, with the blast expected to make landfall over the next 24 hours.

The tropical storm watch was replaced by a hurricane watch west of Intracoastal City, Louisiana, to Port O'Connor, Texas, with hurricane conditions possible within the next 36 hours.

Edouard's center was currently located about 125 kilometres south-south-east of the mouth of the Mississippi River. It was expected to reach the upper Texas coast or the coast of southwestern Louisiana by Tuesday morning.