UPDATE 4-Tropical storm looms off Texas-Louisiana coast

(Updates storm position, oil platforms sustaining high winds)

By Chris Baltimore

HOUSTON, Aug 4 (Reuters) - Tropical Storm Edouard strengthened late on Monday as it churned across the Gulf of Mexico and will likely hit the Texas coast with near-hurricane strength, U.S. forecasters said.

Edouard, the fifth tropical storm of the 2008 Atlantic hurricane season, had maximum sustained winds near 60 mph (97 kph), the U.S. National Hurricane Center said in its 11 p.m. EDT (0300 GMT) report.

Late last month, Hurricane Dolly plowed into Texas with 95 mph (153 kph) winds, dousing the area with tremendous rains and leaving more than 200,000 people without power.

Edouard has a 20 percent chance of reaching hurricane speeds of 74 mph (119 kph) before it makes landfall on Tuesday near or over the upper Texas or Southwestern Louisiana coasts, the Miami-based center said.

The storm, which formed near a major oil- and gas-producing area of the northern Gulf of Mexico on Sunday, was about 105 miles (170 km) south of Lafayette, Louisiana, and 160 miles (260 km) east-southeast of Galveston. It was moving west-northwest at about 8 mph (13 kph).

A tropical storm warning was in effect from the mouth of the Mississippi River in Louisiana to Port O'Connor, Texas, south of Galveston. The center said several elevated oil rigs south of the Louisiana coast have reported sustained winds of 45 to 55 mph (72 to 89 kph).

The storm could cause rain accumulation up to five inches (13 cm) in coastal regions of Louisiana and up to 10 inches (25 cm) in some parts of southeast Texas, U.S. forecasters said.

Texas Gov. Rick Perry declared 17 counties disaster areas and mobilized about 1,200 National Guard troops. In Louisiana, Gov. Bobby Jindal declared a statewide emergency.

Though Galveston's west side could see some flooding, officials on the barrier island are not ordering evacuations.

"Our biggest concerns right now are power outages and street flooding," said Mark Sloan, emergency management coordinator for Harris County. "It shouldn't be that big a deal for us."

OIL OPERATIONS

Edouard, the second named storm to threaten oil operations in the Gulf of Mexico so far this year, shut down a huge offshore oil port, closed the Houston Ship Channel and prompted several offshore operators including Chevron Corp (CVX.N) and Shell Oil (RDSa.L) to evacuate staff from their platforms.

But energy companies reported little production slowdown. The Gulf of Mexico supplies about a quarter of the nation's crude oil and 15 percent of its natural gas, while refiners along the coast produce about a quarter of domestic gasoline.

U.S. crude oil futures hit a three-month low of $119.50 a barrel on Monday before settling down $3.69 at $121.41 a barrel as signs of a slowing U.S. economy and rising supply from OPEC outweighed storm fears.