Mexico emphasizes its stake in U.S. gun policy changes Mexico blames brutal drug violence on guns trafficked from the United States Ambassador: The Second Amendment was not designed to arm foreign criminals He says indignation after the Connecticut school shooting may open "a window of opportunity" Mexican peace activists say the United States has been indifferent to massacres there (CNN) -- Mexicans are watching closely as U.S. President Barack Obama prepares to announce his administration's proposals to stem gun violence. The country's top diplomat in the United States says the tragic Connecticut school shooting may have "opened a window of opportunity" for Obama to fix a problem that has long plagued both sides of the border. "The Second Amendment ... is not, was never and should not be designed to arm foreign criminal groups," Mexican Ambassador Eduardo Medina Mora told reporters last week. His comments were just the latest in years of criticism of U.S. gun policies by Mexican officials, who blame weapons trafficking from the United States and the 2004 expiration of the U.S. assault weapons ban for fueling brutal drug violence south of the border. Now, the issues many Mexicans felt Washington had neglected are in the spotlight. On Wednesday, Obama is scheduled to announce his administration's proposals to crack down on gun violence. And with indignation over guns growing in the United States, reforms that Mexico has long awaited may come through, Medina said. "We hope that there is better regulation," he said. We will keep noting our concerns about this. On Monday, prominent Mexican peace activists renewed their call for the United States to stop weapons trafficking across the border, saying that the Connecticut shooting made the need for action all the more clear. We want to express to you, before anything else, our condolences for the frequent murders of innocents in your country. As parents and grandparents, we were profoundly moved by the massacre of innocent children in Newtown," Mexico's Movement for Peace with Justice and Dignity said in a petition delivered to the U.S. Embassy in Mexico City. "For this same reason," the petition continued, "we are disconcerted and outraged over the indifference of the government of the United States toward the massacres that put Mexico in mourning daily." Most of the weapons used in drug-related violence in Mexico can be traced back to the United States, the group said, citing U.S. government statistics. Nearly 70% of the 99,000 weapons seized in Mexico from 2007 to 2011 came from the United States, the U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives said last year. That issue surged to the fore in Washington last year, amid a U.S. congressional inquiry 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, ATF agents allowed so-called straw buyers to take weapons across the border without being intercepted. Last year, Mexico's government used decommissioned weapons to build a massive sign near the U.S. border that said, "NO MORE WEAPONS." Americans on the other side of the border were the intended audience for the English-language sign, then-President Felipe Calderon said at the time, saying an increase in violence in Mexico was directly connected with the 2004 expiration of the U.S. assault weapons ban. "The criminals have become more and more vicious in their eagerness to spark fear and anxiety in society," he 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.