Pressure mounted on Attorney General Eric Holder Wednesday amid indications that he may have perjured himself over the administration's botched "gun-walking" program.

Questions about what Holder knew and when he knew it grew louder after the attorney general claimed in congressional testimony that he hadn't initially been aware of the "Fast and Furious" operation.

Designed to trace the flow of weapons across the Mexican border, the operation ended up losing track of thousands of guns, which wound up in the hands of drug lords and other criminals.

Some 2,000 firearms at stores in the southwestern United States were illegally sold through the program that allowed "straw purchasers" to walk away with the weapons and turn them over to criminal traffickers.

But federal agents' plan to trace the guns to the cartels never worked. In December 2010, U.S. Border Patrol agent Brian Terry was gunned down by a weapon later linked to the botched gun program.

U.S. Rep. Darrell Issa, R-Calif., turning up the heat on Holder, said the attorney general failed to properly answer questions during a May House Judiciary Committee hearing about when he first learned of Fast and Furious.

“He may or may not have perjured himself, but he certainly failed to answer my questions and [Rep.] Jason Chaffetz’s questions about what did he know -- he implied he knew nothing when, in fact, he at least knew something,” Issa said on Fox News.

“We certainly would like to believe that he was disingenuous but not lying. The fact is, the people who are making those statements on his behalf are lying on his behalf, period."

Issa, who chairs the House Committee on Oversight and Government Reform, has been increasingly critical of Holder, saying the attorney general “had to know” about Fast and Furious from his weekly briefings. Issa cited at least seven separate memos that he said included information about the program.

In addition, Holder’s “No. 2 and No. 3” at the DOJ were “intimately involved,” Issa told Politico.

“This is a man … who, carefully, if he doesn’t like the question, answers it the way he wants to,” Issa said. “He had every obligation to say, ‘I may not have known about all the details but of course I knew about Fast and Furious because I was briefed somewhat on it weekly.’

"He needs to come forward and at least admit that, because, right now, what he said is untrue and he needs to clarify before the committee.”

U.S. Rep. Gus Bilirakis, R-Palm Harbor, is also demanding answers.

"It is extremely troubling that the United States government would willfully allow weapons to be acquired by dangerous criminal and drug-trafficking organizations," the Florida congressman said Wednesday.

"It is also very disturbing to find out that Attorney General Holder and the Obama administration might have known about this program."

Bilirakis last month sent a letter to Holder demanding to know about the roles played by the U.S. Department of Justice and the Bureau of Alcohol, Tobacco, Firearms and Explosives in the failed program.

Congressional investigators told CBS News last month there is evidence the U.S. Attorney’s Office in Arizona sought to cover up a link between “Fast and Furious” and the death of Terry.

"It appears that the DOJ and ATF acted in an extremely misguided manner and that this reprehensible program has resulted in the loss of human life and property," said Bilirakis, who sits on the House Homeland Security Committee.

"To date, the administration has not cooperated with this investigation, but we must get to the bottom of this problem, and that is why I will continue to investigate who knew what about these gun-walking schemes."

A review of government records shows that Deputy Attorney General Gary Grindler participated in an ATF-DOJ briefing about Fast and Furious in March 2010. Grindler is now Holder's chief of staff.

But on May 3, 2011, Holder told the House Oversight Committee he’d only learned of Fast and Furious “over the last few weeks.”

The Justice Department, which Holder oversees, said last month that 30 Fast and Furious weapons were recovered at violent crime scenes in Mexico. The Mexican government maintains that an undisclosed number of Fast and Furious weapons have been found at some 170 crime scenes in that country wracked by narco-crime gangs.

Contact Kenric Ward at kward@sunshinestatenews.com or at (772) 801-5341.