Story highlights Calderon says criminals have "unlimited access to high-powered weapons"

He stands before a new sign in Ciudad Juarez that says, "NO MORE WEAPONS"

The president says Mexico needs U.S. help to stop the violence

Mexico's president called on U.S. officials to stop gun trafficking across the border Thursday, saying the move would be the best thing Americans could do to stop brutal drug violence.

"The criminals have become more and more vicious in their eagerness to spark fear and anxiety in society," President Felipe Calderon said. "One of the main factors that allows criminals to strengthen themselves is the unlimited access to high-powered weapons, which are sold freely, and also indiscriminately, in the United States of America."

Speaking in Ciudad Juarez, the border city across from El Paso, Texas, that has become Mexico's murder capital, Calderon said a dramatic increase in violence in Mexico was directly connected with the 2004 expiration of the U.S. assault weapons ban.

The message was familiar. The Mexican president has asked U.S. lawmakers to renew the ban on assault weapons before, most notably in a 2010 speech to the U.S. Congress.

But the backdrop Thursday was dramatically different. Calderon stood in front of a massive new sign, constructed with tons of decommissioned arms. "NO MORE WEAPONS," the sign said -- in English. Americans on the other side of the border are the intended audience, Calderon said.

"From here, from Ciudad Juarez, on the border of Mexico and the United States, we say, 'No more weapons. No more weapons to Mexico,'" he said.

Thursday's speech came as a U.S. Congressional inquiry continues into "Operation Fast and Furious," an operation run by U.S. federal agents. Authorities have said the operation was intended to track the flow of illegally purchased American guns to the Mexican cartels -- but in practice, agents from the Bureau of Alcohol, Tobacco, Firearms and Explosives allowed so-called straw buyers to take weapons across the border without being intercepted.

Calderon praised U.S. President Barack Obama's efforts to deal with the "very sensitive issue" of assault weapons, noting that officials in his administration had done more than previous leaders to investigate and block illegal weapons trafficking to Mexico.

"They have taken positive steps, but we all know that unfortunately it is not enough, and we cannot stop here," he said.

Out of 140,000 weapons Mexican authorities have seized since Calderon declared a crackdown on cartels at the beginning of his presidency, 84,000 were high-powered assault weapons, Calderon said.

More than 47,000 people have been killed in drug-related violence in Mexico since December 2006, according to government statistics.

During his Thursday speech, Calderon looked toward the border and said he had a message for Americans.

"We need your help to stop this violence. We need you to reduce your consumption of drugs and to dramatically reduce the flow of money to criminal organizations in Mexico," he said. "But beyond the topic of drugs, the best way that you, the American people, can help reduce the violence in Mexico is through legislation that has already been in force in the United States, blocking the inhumane weapons trafficking into our country."