Washington (CNN) -- Top House Republicans attempted to ramp up pressure on Attorney General Eric Holder on Friday with a joint letter demanding the Department of Justice comply with a congressional subpoena for materials on the "Operation Fast and Furious" program.
The sting operation, run by the Bureau of Alcohol, Tobacco, Firearms and Explosives, allowed weapons to be purchased illegally in order to track them to senior drug cartel members, but agents lost track of hundreds of weapons in the process.
"The American people deserve to know how such a fundamentally flawed operation could have continued for so long and have a full accounting of who knew of and approved an operation that placed weapons in the hands of drug cartels," reads the letter signed by House Speaker John Boehner, House Majority Leader Eric Cantor, House GOP Whip Kevin McCarthy and House Oversight Committee Chairman Darrell Issa.
Although the letter acknowledges that there's been some cooperation on the investigation, it emphasizes that House Republicans still want answers in two key areas -- who in top positions knew about the operation before the murder of a federal border agent exposed its existence, and did anyone on Holder's team misinform Congress when they responded in part to the Oversight committee's subpoena.
The leadership letter comes as rank-and-file conservatives grow openly frustrated that the Department of Justice refuses to give over some documents and is pushing their leaders to show a harder line with the administration. A group of six freshmen on the House Judiciary Committee sent GOP leaders a letter late Thursday pushing them to move forward with a House vote on a resolution holding Attorney General Eric Holder in contempt of Congress for failing to produce the full list of materials Issa's committee asked for months ago.
"It's time for the House to formally recognize the obvious -- that Attorney General Holder has not and will not cooperate with the legitimate investigation launched by the House Oversight and Government Reform Committee and is therefore in contempt of Congress," the freshmen lawmakers wrote Thursday.
Issa, who already circulated a draft contempt resolution earlier this month signaling he was losing patience, stressed that Friday's letter demonstrates that leaders are on the same page as he is about arguing that Congress has a right to get the information.
Boehner also raised the issue directly with President Obama at a White House meeting on Wednesday, urging him to get Holder to respond to the congressional requests.
Although the Friday letter to Holder does not specifically warn the House will move to a contempt vote if they don't get the materials, it does come close.
"As co-equal branches of the U.S. Government, the relationship between the Legislative and Executive branches must be predicated on honest communications and cannot be clouded by allegations of obstruction. If necessary, the House will act to fulfill our Constitutional obligations in the coming weeks," the leaders wrote.
Issa conceded that some of his Republican colleagues are anxious for a vote. He said he's already circulated a draft resolution laying out the details of what the committee still wants from the Justice Department. But Issa also stressed "our goal is not to have a vote to hold the attorney general in contempt. Our goal is to have cooperation on behalf of the American people -- something the attorney general promised us."
Holder and key aides were en route to Washington from Europe following a weeklong series of meetings, so were unable to immediately respond to the letter.
But the Justice Department has responded to similar requests from congressional Republicans by noting they have already turned over tens of thousands of pages of documents. Justice has also maintained that many of the materials the GOP continues to press for are sensitive and could potentially jeopardize ongoing prosecutions related to "Fast and Furious."
CNN Justice Producer Terry Frieden contributed to this report.