In a speech to a joint session of Congress, Calderon described efforts to fight organized crime in Mexico, where 23,000 people have been killed in drug violence since he came to power in late 2006 and launched an army offensive.
Washington is also aiding Mexico's battle against drug gangs with a 2007 pledge of $1.4 billion for equipment and police training to help fight the cartels that ship some $40 billion worth of illegal drugs north each year.
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 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.
Calderon said he respects Americans' Second Amendment right to bear arms but said many of the guns are getting into the hands of criminals.
More here: Calderon urges U.S. to reinstate assault weapons ban - Yahoo! News