Police in Texas have seized a cache of weapons allegedly being smuggled to drug gangs in Mexico.
The haul, in Laredo on the US-Mexico border, included assault rifles and thousands of rounds of ammunition.
Police say it was one of the largest weapons shipments found in recent years. Two men have been arrested.
The seizure comes two weeks after Mexican President Felipe Calderon urged US lawmakers to help stem the flow of weapons to Mexico.
Texas police say they acted on a tip-off and stopped a truck. Inside, they found 147 assault rifles, 53 bayonets and more than 10,000 rounds of ammunition they believe were heading across the border to Mexico.
"This is one of the biggest cases we've ever seen here in this city," Laredo police officer Alberto Escobedo told Reuters.
"It's a tremendous blow to drug traffickers and organised crime."
In a speech to Congress last month, President Calderon said 75,000 weapons had been seized in three years - and 80% of those that could be traced had come from the US.
President Obama has said that US demand for drugs has contributed to the violence in Mexico, and that the flow of guns from the US to Mexico must be stopped.
Drug-related violence in Mexico has left some 23,000 people dead since President Calderon came to office in December 2006 and launched a crackdown on drug gangs.