A US plan to help curb drug trafficking in Mexico by requiring US gun dealers to record certain weapons sales faced mounting criticism from the governor of Texas and the National Rifle Association.
The US Bureau of Alcohol, Tobacco, Firearms and Explosives said earlier this week that it would ask US gun dealers in the border states of Texas, Arizona, California and New Mexico to report "multiple" sales of semi-automatic rifles.
But the plan, which aims to curb the large number of US-purchased assault weapons used in Mexico's violent drug war, has been lambasted by gun rights advocates.
They say the reporting requirements violate the Second Amendment of the US Constitution, which provides the legal underpinnings for gun ownership.
"Instead of arbitrarily implementing this misguided and constitutionally questionable policy, the Obama administration should target actual criminals rather than law-abiding citizens," Texas Republican Governor Rick Perry said Wednesday.
"Targeting legal gun sales and sellers will have little or no impact on the Mexican cartels transporting drugs, guns and cash to and from major cities throughout the US," Perry said.
The nation's biggest gun lobby, the National Rifle Association has said it planned to contest the new policy in court.
"ATF and the administration lacks the statutory authority to do this and the NRA will file suit as soon as ATF sends the first demand letters," said the group's director, Chris Cox, in a statement.
Cox said the Obama administration was merely trying to divert attention from the embarrassing failure of an ATF plan known as "Fast and Furious."
That operation was intended to build cases against Mexican gang members by knowingly allowing them to purchase assault weapons in the United States, then tracing those weapons to crime scenes in Mexico.
Most of the weapons, however, were never traced, while two of them showed up at the murder site of a US border patrol agent, which led to the program's suspension.
"It is the height of hypocrisy for the Obama administration to restrict the gun rights of border state citizens, when the administration itself knowingly and intentionally allowed guns to be trafficked into Mexico," said Texas Republican Representative Lamar Smith.
In Mexico City, Foreign Minister Patricia Espinosa applauded the US move, but said more was needed.
"Mexico recognizes the effort on the part of the US government, we recognize it as a positive step in the right direction," Espinosa told a press conference. "But we continue to reaffirm the importance of the United States stopping illegal trafficking of weapons into our country."
Experts say that in the regions of US states that run along the Mexican border there are some 9,000 gun stores.
More than 50,000 soldiers have been deployed across Mexico by Mexican president Felipe Calderon to fight drug gangs since he took office in December 2006.
In total more than 37,000 people linked to drug trafficking have been killed in Mexico since then, either in battles between cartel members or with the military.