MEXICO CITY - Mexico's state oil company Pemex has discovered oil at the Leek-1 well in the deep waters of the Gulf of Mexico and is testing it to see if it is commercially viable, a Pemex spokesman said on Thursday.

Leek is the first oil discovery Pemex has made this year in the deep waters of the Gulf of Mexico and follows the Tamil oil discovery in the Gulf in 2008, which Pemex declared commercial earlier this year.

Pemex has drilled four wells in the deep water this year, finding natural gas with the Holok well. Two other wildcats, Cox and Catamat, were dry holes.

The company is stepping up its exploration efforts in the Gulf of Mexico as it scrambles to find new fields to replace the aging giant Cantarell field, where production has been plunging.

Two new deepwater drilling rigs will start working for Pemex in 2010, boosting exploration efforts.

Pemex is working on developing the Tamil discovery as part of a cluster of oil fields in the Gulf of Mexico by the middle of the next decade. The Gulf's Lakach natural gas field is also slated for development. (Reporting by Robert Campbell; Editing by Christian Wiessner)