Congress and the Department of Justice appear to be headed for a showdown this week over documents detailing Operation Fast and Furious, the botched gunrunning sting set up by the Bureau of Alcohol, Tobacco, Firearms and Explosives that funneled more than 1,700 smuggled weapons from Arizona to Mexico.

The Justice Department has until Wednesday to deliver to congressional investigators a stack of records and emails naming the individuals responsible for the gun trafficking operation that may have killed dozens, if not hundreds of Mexicans, and is becoming a growing embarrassment for the Obama administration.

Under Project Gunrunner and the Phoenix off-shoot, dubbed Fast and Furious, the ATF encouraged gun store owners to sell to straw buyers -- consumers who they suspected of working on behalf of Mexican drug cartels.

Project Gunrunner purposely allowed the straw buyers to illegally buy and export guns only to see where they surfaced in Mexico. Using this investigative technique, the ATF hoped to take down the entire gun trafficking organization. Instead, records show it allowed more than 1,700 guns, including hundreds of AK-47s and high-powered, armor-piercing .50-caliber rifles to be trafficked to Mexico

Buying guns for non-personal use is illegal. Yet gun store owners were assured by ATF agents the buyers were under investigation and the guns were being intercepted before crossing into Mexico.

Instead, whistleblowers say the guns were allowed "to walk."

President Obama, speaking for the first time about the growing scandal, conceded last week Fast and Furious may have been "a serious mistake," but he claimed, "I did not authorize it; Eric Holder, the attorney general, did not authorize it. He's been very clear that our policy is to catch gunrunners and put them into jail."

But an investigation by Rep. Darrell Issa, R-Calif., chairman of the House Committee on Oversight and Government Reform, could show otherwise.

The ATF operates under Justice Department, and two assistant U.S. attorneys in Phoenix authorized virtually every wiretap, affidavit and investigation conducted in Operation Fast and Furious.

Some, like Issa, wonder how Holder could not have known about an investigation that size.

"One of the questions we always ask is who is lying," Issa told Fox News. "We lose our credibility if we don't come clean and make the changes necessary to save lives on both sides of the border."

If the Justice Department and ATF refuse to deliver the records Issa requested, as it already has done with similar requests by Sen. Charles Grassley, R-Iowa, Issa can subpoena the records.

"We will subpoena if we have to, we'll hold hearings if we have to, we'll call in officials if we have to. But at the end of the day, the two Americans likely to have died as a result of this action pale in comparison to the countless numbers of Mexicans who have been killed," said Issa.

He is referring to Border Patrol Agent Brian Terry and Immigration and Customs Enforcement Agent Jamie Zapata. The guns used to kill both men were bought in the U.S. and investigators will now see if they are linked to Project Gunrunner.

Humberto Trevino, a senior Mexican lawmaker, says at least 150 people have been shot with ATF-monitored guns.

Two of the gun stores involved were Carter's Country in Houston and J&G Gun Sales in Prescott, Ariz.

"Let me tell you something about Carter's Country. They have been co-operating with ATF from the get-go," says Carter's County attorney Dick Deguerin.

"They were told to go through with what they considered to be questionable sales. They were told to go through with sales of three or more assault rifles at the same time or five or more 9-mm guns at the same time or a young Hispanic male paying in cash. It's all profiling, but they went through with it."

Both gun stores felt burned by the ATF -- first by leaked records to The Washington Post that showed the two stores responsible for dozens of guns found at Mexican crime scenes, and now by Operation Fast and Furious.

"You assumed they had your back," added J&G President Brad Desaye. "Absolutely, we felt like partners with ATF in a lot of ways."

Assistant Attorney General Ronald Weich said in a Feb. 4 letter the operation's purpose was "to dismantle the entire trafficking organization, not merely to arrest straw purchasers."

"The allegation -- that ATF 'sanctioned' or otherwise knowingly allowed the sale of assault weapons to a straw purchaser who then transported them into Mexico -- is false," he wrote.

Holder also says his department policy is not to "let guns walk."