FACTBOX: Gustav threatens U.S. Gulf oil, gas, commods

(Reuters) - Forecasters say Hurricane Gustav could be the first major threat to the U.S. Gulf of Mexico oil fields and ports since hurricanes Katrina and Rita in 2005.

The Gulf is the source of 25 percent of domestically produced oil and 15 percent of the natural gas. More than a third of U.S. refining capacity is on the U.S. Gulf Coast.

At the center of the "cone of uncertainty" is New Orleans, a major port handling raw materials and foodstuffs. The Port of South Louisiana is the nation's largest in tonnage handled.

Both Katrina and Rita were Category 5 storms, top of the hurricane intensity scale. Katrina hit New Orleans in August 2005. Rita hit near the Texas-Louisiana line that September.

Gustav, expected to come ashore Tuesday on the Gulf Coast, is forecast as Category 3, still potentially catastrophic.

---- IMPACTS OF GUSTAV ----

- The U.S. Minerals Management Service said Friday the threat of Gustav had shut 86,013 barrels per day of oil production (6.62 percent) and 136 million cubic feet per day of natural gas output (1.84 percent) in the Gulf.

- Crude oil shot up $3 in early trading on the New York Mercantile Exchange Friday on fears of storm-related output cuts before settling down 13 cents at $115.46 a barrel. Products also rallied

- The U.S. Environmental Protection Agency said it was waiving the summer blend requirements to ease gasoline supply in coastal Louisiana.