Mexico on Thursday accused US gunmakers of "clear negligence" following the massacre of 19 children and two teachers at an elementary school in Texas.
The violence-plagued Latin American nation is suing firearms manufacturers in the United States over cross-border weapon smuggling.
"There's clear negligence on the part of this industry," Mexican Foreign Minister Marcelo Ebrard told reporters.
"For a young man to be sold an assault weapon at the age of 18 leads to this kind of tragedy," he added.
Salvador Ramos, 18, used a legally bought AR-15 military-style assault rifle in Tuesday's attack that shook a tight-knit Latino community in the town of Uvalde near the border with Mexico.
Last August, the Mexican government filed an unprecedented lawsuit against major US gunmakers in a Boston court over illegal arms flows that it blames for fueling drug-related violence.
The National Shooting Sports Foundation, the US firearm industry trade association, has called the litigation "an affront to US sovereignty" and said Mexico was responsible for crime within its borders.
