Jury selection began in Phoenix on Tuesday in the trial of a U.S. gun dealer charged with knowingly selling hundreds of weapons to smugglers shopping for Mexican drug cartels.

Prosecutors say George Iknadosian, 47, sold AK-47 assault rifles and other guns to third-party buyers for the cartels in Mexico, where 6,000 people were killed in drug violence last year.

Iknadosian denies the charges.

Since 2006, Mexico has sent tens of thousands of troops to fight powerful cocaine cartels locked in a bloody war for control of lucrative cross-border smuggling routes to the United States.

Gun sales are illegal in Mexico. Investigators say nine out of every 10 guns recovered from Mexican crime scenes are traced back to U.S. gun dealers, prompting Mexican authorities to urge the United States to crack down on the trade.

After an 11-month effort by Mexican authorities and the U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives to curb gunrunners, they nabbed Iknadosian.

ATF said third parties, known as "straw purchasers," were paid by smugglers working for the cartels to buy guns at Iknadosian's X-Caliber Guns store in north Phoenix. The straw purchasers were paid $100 a gun, ATF said.

The weapons were then spirited south of the border to arm drug cartels in Mexico's Sonora and Sinaloa states, ATF said.

Some of the weapons sold in Iknadosian's shop have been traced to crimes in Mexico. One pistol was recovered in January 2008 when Mexican police arrested Alfredo Beltran Leyva, a top lieutenant of Joaquin "Shorty" Guzman, Mexico's most wanted fugitive who leads a powerful cartel from Sinaloa.

Concern over Mexican drug cartel violence has grabbed headlines in the United States in recent days.

U.S. Senate lawmakers announced last week they would hold hearings to assess the ability of U.S. security forces to handle the rise in crime on the U.S. side of the border related to Mexican traffickers.

Mexican authorities have ordered thousands of additional troops to restore order in Ciudad Juarez, just south of El Paso, Texas, where more than 2,000 people have been killed since the start of last year.