A U.S. Border Patrol agent has pleaded guilty to trafficking more than one tonne of marijuana and using his patrol vehicle to transport it, prosecutors said on Thursday. Agent Juan Luis Sanchez, 31, pleaded guilty at the U.S. District Court in Tucson, Arizona, to possession with intent to distribute 1,000 kilograms or more of marijuana, the U.S. Attorney's office said in a news release.

Sanchez admitted he used his patrol vehicle on six separate occasions to transport marijuana in the area around Nogales, in southern Arizona on the border with Mexico, and to accepting $45,000 in bribes.

The agent also pleaded guilty to worker's compensation fraud charges relating to an injury he received in a vehicle accident while on duty.

Sentencing in the case was set for Aug 13. Sanchez faces a fine of up to $4 million and a maximum penalty of life in prison.

Southern Arizona is the busiest corridor for marijuana smuggling on the nearly 2,000-mile (3,200-km) U.S.-Mexico border.

Last year, Border Patrol agents in the Tucson sector seized some 440 tons (tonnes) of the drug, which is moved over the border by smugglers in trucks, on horseback and on foot in improvised backpacks.