(Updates with production impact, details, quote)

MEXICO CITY, Aug 19 (Reuters) - Mexico has started to evacuate 13,360 workers from its Gulf of Mexico oil rigs as powerful Hurricane Dean neared and the move will affect production, state oil company Pemex said on Sunday.

Pemex, which produces some 70 percent of its crude oil from offshore platforms in the Gulf of Mexico and is a major supplier to the United States, said it would know the output impact early on Monday.

"Production is currently normal, but this (the evacuations) will affect production. We will have an idea (of how much) early on Monday," a Pemex spokeswoman said in the Mexican capital.

Pemex said it aimed to finish its evacuations before noon (1600 GMT) on Monday.

Mexico, the world's No. 5 oil producer by volume, operates hundreds of rigs in the Gulf of Mexico at oil fields like Cantarell and Ku Maloob Zaap. It also produces a third of its natural gas in the offshore region.

The bulk of Mexico's crude oil exports are shipped through the Mexican Gulf from Dos Bocas, Cayo Arcas and Pajaritos ports. The ports are still open, Mexico's government said.

The last storm to seriously disrupt Mexico's oil industry was in July 2005, when Pemex had to evacuate thousands of rig workers, temporarily cut off oil production from dozens of rigs and briefly halted shipments due to Hurricane Emily.

AlertNet news is provided by