Slow-moving Tropical Storm Lee strengthened as it lumbered toward the Louisiana coast on Saturday, bringing torrential rains that will put the flood defenses of low-lying New Orleans to the test.

The storm is expected to reach the Louisiana coast later on Saturday and bring 10-15 inches (25-38 cm) of rain to southeast Louisiana over the next few days, including to New Orleans, which was battered by Hurricane Katrina in 2005, the US National Hurricane Center said.

Early on Saturday, Lee was 15 miles (25 km) south-southeast of Intracoastal City, with maximum winds of 60 miles per hour (95 kph), the hurricane center said. Lee's winds were expected to stay below the 74 mph (119 kph) threshold of hurricane strength.

But the prospect of flooding in low-lying New Orleans evoked memories of Hurricane Katrina, which flooded 80 percent of the city, killed 1,500 people and caused more than $80 billion in damage.

Lee was just expected to spur localized flooding in coastal and low-lying areas, New Orleans officials said.

The city's extensive levee system is capable of processing about one inch of rainfall per hour, but the storm's slow-moving nature could bring challenges, officials said.

'The extended rainfall changes the dynamic a bit and makes it harder to manage over the course of the weekend,' said Craig Taffaro, St. Bernard Parish president, speaking on local television.

Low-lying parishes around New Orleans saw rising waters, which covered some roadways in Plaquemines and St. Bernard parishes, but no homes or businesses were threatened.

'We need to get this thing onshore and get it through here,' Plaquemines Parish president Billy Nungesser told local television.

Lee will weaken once it hits land, but it will lose strength more slowly than normal due to the marshy nature of the Louisiana coast, the hurricane center said.

Lee's northeasterly track could bring heavy rains to Mississippi, Alabama, Georgia, Tennessee and the Appalachian Mountains next week.

Major offshore producers like Royal Dutch Shell, Exxon Mobil Corp and BP Plc shut down platforms and evacuated staff earlier this week.

About half the US offshore oil production, all based in the Gulf of Mexico, and a third of offshore gas production were shut as of Friday, according to the US government. Most of that output should quickly return once the storm passes.

Louisiana Governor Bobby Jindal on Friday warned that heavy rains, substantial winds and tidal surges from the Gulf of Mexico could produce flash flooding in parts of New Orleans throughout the Labor Day holiday weekend.

'Get ready for the wind, get ready for the rain, it's coming and it's going to be here for a while,' Jindal said at a briefing in Baton Rouge. Jindal has declared a state of emergency for Louisiana, and Mississippi Governor Haley Barbour made a similar ruling for seven coastal counties. – Reuters