A judge has started the process to extradite Julian Zapata Espinoza, a suspected member of the Los Zetas drug cartel arrested in connection with the February killing of a U.S. Immigration and Customs Enforcement, or ICE, agent in the central Mexican state of San Luis Potosi, to the United States, the Attorney General's Office said Tuesday.

Zapata Espinoza, who was arrested on Feb. 23, will not be charged in Mexico to clear the way for his possible handover to the United States, the AG's office said.

The suspected Zetas cartel member is wanted by U.S. authorities for the Feb. 15 killing of ICE agent Jaime Zapata, the AG's office said.

The United States requested Zapata Espinoza's extradition on May 12 "for his probable role in the homicide of a special agent" of ICE, the AG's office said in a statement.

The suspect was transferred two days later to the federal prison in Villa Aldama, a city in Veracruz state, where he will be held until the extradtion case is completed.

Zapata and fellow ICE agent Victor Avila, who was wounded, were attacked by gunmen working for the Los Zetas drug cartel while driving from Mexico City to the northern city of Monterrey.

The two agents, who were assigned to the ICE attache office in Mexico City, were driving an armored vehicle when they were attacked in San Luis Potosi.

Jaime Zapata's killing sparked a debate in Mexico over whether U.S. agents should be allowed to carry weapons to defend themselves.

President Felipe Calderon said during his visit to Washington on March 3 that "alternatives" would be examined with Congress to improve the security of U.S. agents working in Mexico.

"We want them to have the best conditions for their security," Calderon said in a press conference, acknowledging that "there are very important legal restrictions" on what foreign law enforcement agents may do in Mexico.

Zapata Espinoza, who has admitted that he was the leader of a Zetas cell, told investigators that the U.S. agents were attacked by mistake.

The 32-year-old Zapata, who was laid to rest Feb. 22 in Brownsville, Texas, was on a temporary assignment in Mexico.

Mexican authorities have detained several people, all suspected members of Los Zetas, in connection with the attack.

About 30 ICE agents are currently working in Mexico, according to the agency, along with others from the Drug Enforcement Administration and the FBI, with agents assigned to Mexico City and other cities, such as Monterrey, Hermosillo, Guadalajara, Ciudad Juarez and Durango.