. . .The drug violence has become a major political test for Calderon and a growing worry for Washington and foreign investors as violence has spread across the southwest border.

“There is one issue where Mexico needs your cooperation. And that is stopping the flow of assault weapons and other deadly arms across the border,” Calderon said to a standing ovation from U.S. lawmakers.

Calderon said the increase in violence in Mexico had coincided with the 2004 lifting of a U.S. assault weapons ban.

The 10-year ban on the sale of assault weapons to civilians expired without being extended by Congress. Attorney General Eric Holder has said the administration favors reinstituting the ban, though guns rights groups oppose it.