Congress to hold hearings on Mexican drug violence

US Attorney General calls drug cartels 'a threat to national security'

Walters praised U.S. training and assistance programs for Mexico in the field of personnel protection and the creation and vetting of special federal squads to go into areas where the state and local police might have been bought off or cowed by the cartels.

The violence has "not yet been turned against significant members of the Mexican government," said Walters. "We are trying to help the government as they train and equip more of their institutions to protect these individuals."

There were areas of the country where local and even state police were "suborned, being used as assassins and enforcers and foot-soldiers" by the cartels. For such circumstances, Mexico was developing, with U.S. assistance, "specially trained and vetted groups - both military and police" who could take over law and order responsibilities.

The Senate committee statement said, "Other issues that may arise include - the value of deploying the National Guard - and the potential for mass migration northward."

Most experts dismiss the possibility of state collapse or other developments in Mexico that might lead to such mass migration.

"It's not helpful to talk in terms of state collapse," said Walters, who was not commenting on the committee statement. "That kind of talk is not only uncalled for but weakens the sense that both American and, I believe, Mexican citizens have that they support each other."