WASHINGTON, Feb 2 (Reuters) - Republicans in the U.S. House of Representatives said on Thursday senior Justice Department officials should have known about the controversial tactics that led to a bungled operation to track guns to Mexico because some details were practically at their fingertips.

President Barack Obama's administration has been under fire for almost a year over the operation dubbed "Fast and Furious," which was meant to determine how guns were being smuggled from Arizona to violent drug cartels.

But U.S. government agents lost track of many weapons. While as many as 2,000 weapons were sold by gun dealers to people believed to be straw purchasers for Mexican drug cartels, fewer than 600 had been recovered as of January 2011.

The operation, which ran from late 2009 until early 2011, came to light after two weapons from it were found in Arizona in December 2010 near the scene of a shootout with illegal immigrants that left U.S. Border Patrol agent Brian Terry dead.

The chairman of the House Oversight Committee, Republican Representative Darrell Issa, issued a memorandum detailing how other federal authorities were already tracking the drug cartel gun smugglers a year before Terry was killed.

He and other Republicans on the panel said at a hearing that senior Justice Department officials should have known guns were being trafficked without adequate surveillance from wiretap applications and details they had about a similar sting during the Bush administration known as "Wide Receiver."

"All of those people should be ashamed that Brian Terry is dead because they didn't do as good of a job as they should," Issa said during the hearing.

Several Republicans on the committee also expressed disbelief that senior Justice Department officials were unaware of the operation. "To say that we didn't really know about it to me is absolutely preposterous and that's something that I can't accept," said Representative Mike Kelly from Pennsylvania.

U.S. Attorney General Eric Holder repeated to the panel that allowing guns to go across the border unmonitored was wrong, but he and other senior officials at the Justice Department and Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) were in the dark until the operation had ended.

"It's unacceptable, it's stupid, it's dangerous and not something that this Department of Justice can ever do," Holder told the panel, referring to the tactics used in the operation.

RANCOROUS EXCHANGE

The hearing got testy when Republicans questioned Holder's honesty and integrity. New York Republican Ann Marie Buerkle asked "how many more border patrol agents would have had to die as a part of operation Fast and Furious for you to take responsibility?"

Holder became especially angry when Republican Raul Labrador of Idaho brought up unrelated partial remarks he had made more than a decade ago about his involvement in the pardon of financier Marc Rich during the Clinton administration.

"Have I been perfect? No. Have I made mistakes? Yes. Do I treat the members of this committee with respect? I always hope that I do. And what you have just done is, if nothing else, disrespectful," Holder said.

Some Republicans have called for Holder's resignation but he received support from President Barack Obama after the hearing. "He absolutely stands by the Attorney General, thinks he is doing an excellent job," White House spokesman Jay Carney said.

The attorney general told lawmakers he expected to hold people accountable in a court of law for Terry's murder within six months and possibly by the end of March. He also said whoever authorized the tactics would likely be fired.

Republicans expressed frustration that it was taking so long for disciplinary action.

"You told people that you were mad, you were upset. That to me is silly. You've not taken action, you've not fired anybody," said Representative Patrick McHenry of North Carolina.

Holder said further action against those responsible would have to wait for the Justice Department's inspector general to finish her investigation and report, he said.

"To the extent that we find out who precisely was involved in this or who gave that order, I can assure you that unless there is some truly compelling circumstance, that person, those people, will be removed from federal service," Holder said.

Earlier this week, the family of the slain Border Patrol agent filed a $25 million wrongful-death claim against the U.S. government, saying he was killed because federal investigators allowed guns to fall into the hands of violent criminals.

(Reporting by Jeremy Pelofsky; Additional reporting by James Vicini, Laura MacInnis and Tim Gaynor)

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