|Republican senators accused Eric Holder of not doing enough to stop the flawed operation [EPA]
The US attorney-general has expressed regret that the country’s justice department misled legislators about the allegations of serious problems in the controversial arms trafficking investigation called Operation Fast and Furious.
At a Senate Judiciary Committee hearing on Tuesday, Eric Holder said that the probe was flawed in concept as well as in execution, never should have happened and "it must never happen again".
The operation, conducted in 2009, employed a now-controversial investigative tactic known as gun-walking. Several federal agents said they were ordered to let suspected straw buyers walk away from Phoenix-area gun shops with AK-47s and other weapons believed headed for Mexican drug cartels.
"The goal of the United States was that these guns would lead them to Mexican drug cartel leaders and they could work with Mexican authorities to pursue arrests," Al Jazeera's Kimberly Halkett, reporting from Washington, said.
She said legislators were questioning the attorney-general about what he knew of the operation and when he had learned of its wrong turn.
"Allegations [have been] made by the Senate Republicans that, in fact, the attorney-general knew about the operation far earlier than he is revealing, according to emails that have been made public - and that he did little to stop it before it was too late."
But Holder, the butt of criticism in the congressional investigation into the justice department's handling of the operation, says he learned of problems in Fast and Furious earlier this year.
About 1,400 of the 2,000 guns went missing, two of which turned up at the scene of a shootout in Arizona that resulted in the death of Brian Terry, a Customs and Border Protection agent.
Holder expressed regret to Terry’s family.
Holder's comments came as the panel's top Republican Senator, Charles Grassley, said the operation represented an "utter failure" by federal law enforcement officials to enforce existing gun laws.
Grassley asked who the attorney-general "plans to hold accountable" for the arms trafficking probe.
Holder said he wanted to know why and how firearms that should have been under surveillance could end up in the hands of Mexican drug cartels.
Al Jazeera's Adam Raney, reporting from Mexico City, said there was not much direct reaction to Holder's comments, but, in the past, Mexican officials have repeatedly expressed concern about guns coming over from the US.
"Officials in the past have said that a lot of the drug violence here is as a result of guns from the US."
He said even Holder acknowledged that from about 94,000 guns studied in Mexico, 64,000 had been traced back to the US.
Felipe Calderon, the Mexican president, has said that much of the violence in Mexico is easily attributable to guns from the US.
In August, the justice department replaced three officials who played critical roles in the arms trafficking probe. The department's inspector general is still investigating the case - at Holder's request.
Holder said that "unfortunately, we will feel its effects for years to come as guns that were lost during this operation continue to show up at crime scenes both here and in Mexico".