Washington (CNN) -- Kenneth Melson, acting director of the Bureau of Alcohol, Tobacco, Firearms and Explosives, is expected to resign under pressure, perhaps in the next day or two, in the wake of the controversy over Operation Fast and Furious, two senior federal law enforcement sources said Monday.

In the operation, straw buyers were allowed to purchase illegally large numbers of weapons, some of which ended up in the hands of cartels in Mexico.

Attorney General Eric Holder will meet Tuesday with Andrew Traver, head of the ATF field office in Chicago, about possibly becoming the agency's acting director, according to senior federal law enforcement sources, who are familiar with the details of the controversy.

The Justice Department refused comment. White House press secretary Jay Carney told reporters he had no new information on the issue.

The operation has come under intense criticism since the December killing of a U.S. Border Patrol officer.

Operation Fast and Furious was "a colossal failure of leadership," Peter Forcelli, a supervisor at the bureau's Phoenix field office, said recently.

The program focused on following people who legally bought weapons that were then transferred to criminals and destined for Mexico. But instead of intercepting the weapons when they switched hands, Operation Fast and Furious called for ATF agents to let the guns "walk" and wait for them to surface in Mexico, according to a report by the House Oversight and Government Reform Committee.

The idea was that once the weapons in Mexico were traced back to the straw purchasers, the entire arms smuggling network could be brought down. Instead, the report argues, letting the weapons slip into the wrong hands was a deadly miscalculation that resulted in preventable deaths, including that of Border Patrol Agent Brian Terry.

Terry was killed last year north of the Mexican border in Arizona after confronting bandits believed to be preying on illegal immigrants. Two weapons found near the scene of the killing were traced to Fast and Furious.

"I was flabbergasted. I couldn't believe it at first," Terry's mother, Josephine, said when she learned the ATF may have let some of the guns used in the attack slip through its fingers. Terry's relatives said they want all those involved in his killing and who helped put the weapons in their hands to be prosecuted.

"We ask that if a government official made a wrong decision, that they admit their error and take responsibility for his or her actions," Robert Heyer, Terry's cousin and family spokesman, said in a hearing last week by the House panel.

The committee's chairman, Rep. Darrell Issa, R-California, called the operation "felony stupid." As many as 2,000 semiautomatic rifles reached the hands of cartels as a result, and Issa said the top two ATF officials were briefed on the program regularly.

In Mexico, the case has drawn nationwide attention and sharp criticism from top officials, who have long stressed that U.S. weapons are fueling the country's drug war.

The Mexican attorney general's office demanded a quick U.S. investigation of the matter in March and said authorities must hold accountable anyone who was responsible for the operation.

"As the United States government has signaled, the government of Mexico was not informed of any operation that would include the controlled transport of weapons to Mexico," the office said.