HOUSTON - Ida weakened to a tropical storm as it churned toward oil and gas facilities in the Gulf of Mexico and was forecast to hit the U.S. Gulf Coast early on Tuesday, the U.S. National Hurricane Center said on Monday.

Ida was expected to come ashore somewhere between Louisiana and Florida. At its earlier hurricane strength, Ida triggered floods and mudslides that killed 124 people in El Salvador.

Ida's top sustained winds dropped to 70 miles per hour, and the storm is unlikely to regain hurricane strength before it makes landfall, U.S. forecasters said.

Ida posed the first real storm threat of the 2009 hurricane season to Gulf of Mexico oil and natural gas production, and forced some companies to shut down off-shore platforms and evacuate personnel.

Oil rose more than $1 to above $79 a barrel on Monday on fears that Ida would cut U.S. oil and gas supplies.

The Louisiana Offshore Oil Port, the only U.S. terminal capable of handling the largest tankers, stopped unloading ships due to stormy seas. The Independence Hub, a major offshore natural gas processing facility, also was closed.

A quarter of U.S. oil and 15 percent of its natural gas are produced from fields in the Gulf and the coast is home to 40 percent of the nation's refining capacity.

LOUISIANA STATE OF EMERGENCY

The Miami-based hurricane center discontinued hurricane warnings along the U.S. Gulf Coast, and said a tropical storm warning was in effect from Grand Isle, Louisiana, to Aucilla River, Florida.

The tropical storm warning included the city of New Orleans, which is still recovering from the devastation of Hurricane Katrina in 2005.

Louisiana Governor Bobby Jindal declared a state of emergency on Sunday, allowing the government to mobilize troops and rescue workers.

The hurricane center earlier on Monday had downgraded Ida from a Category 2 hurricane to Category 1, the lowest rank on the five-step Saffir-Simpson intensity scale, before further downgrading it to a tropical storm.

In El Salvador, rivers burst their banks and hillsides collapsed under relentless rains triggered by Ida's passage, cutting off parts of the mountainous interior from the rest of the country.

The bulk of the Central American country's coffee is grown in areas far from the worst affects of the flooding but the national coffee association had no estimate of potential damage to the harvest.

Ida swept past the Mexican resort of Cancun on Sunday, inflicting little damage. Ida first became a hurricane on Thursday off the Caribbean coast of Nicaragua, where heavy rains forced more than 5,000 people into shelters.

The country's coffee crop was not directly affected by the storm, according to the local coffee council.

(Additional reporting by Jose Cortazar and Michael O'Boyle in Cancun, Nelson Renteria in San Salvador, Ivan Castro in Managua and Erwin Seba in Houston; Editing by Will Dunham)

Florida Storm