A Border Patrol chief at one of the nation's most dangerous Southwest border crossings says the agency's mission doesn't include apprehending illegal aliens or seizing narcotics — perplexing front-line agents and angering a congressional critic of illegal immigration.

"I've said it before and I'll say it again," Carlos X. Carrillo, Border Patrol chief of Laredo, Texas, told guests at a town-hall meeting Thursday. "The Border Patrol's job is not to stop illegal immigrants. The Border Patrol's job is not to stop narcotics. ... The Border Patrol's mission is not to stop criminals.

"The Border Patrol's mission is to stop terrorists and terrorist weapons from entering the country."

Law-enforcement agencies consider Laredo to be one of the Southwest's most dangerous border crossings. It is the sister city of Nuevo Laredo, Mexico, which is controlled by one of that country's most ruthless drug-smuggling rings.

Rep. Tom Tancredo, Colorado Republican, called for Mr. Carrillo's resignation Friday. He also questioned how the recently appointed official could tell the difference between an illegal alien and a terrorist.

"If the Border Patrol has developed a new technology that can distinguish between terrorists and other illegal border crossers without first catching them and checking them out, that is good news," said Mr. Tancredo, an outspoken critic of illegal immigration and a presidential candidate. "But if that is not the case, Mr. Carrillo's statements are extremely irresponsible and demoralizing to officers in the field."

Rep. Tom Tancredo, Colorado Republican, called for Mr. Carrillo's resignation Friday. He also questioned how the recently appointed official could tell the difference between an illegal alien and a terrorist.