Washington ( CNN ) -- An intense struggle among several senior Justice Department officials was revealed Friday as internal documents on the gun-running Operation Fast and Furious were released by the department . About 1,400 pages that had been demanded by Capitol Hill investigators were sent to three key congressional committees in advance of what is expected to be a contentious hearing next Thursday when Attorney General Eric Holder testifies on the subject . The documents lift the veil on conflicting views among Justice Department executives , the Bureau of Alcohol , Tobacco , Firearms and Explosives ( ATF ) , and the Arizona U.S. attorney 's office over whether and how to respond to allegations made in letters from Sen. Charles Grassley , R-Iowa . Grassley had demanded to know whether , as whistle-blowers claimed , the ATF was allowing firearms bought by suspected straw purchasers in Arizona to `` walk '' across the border into Mexico , and into the arms of drug cartels . Grassley had alleged the ATF 's surveillance operation lost track of weapons and two of them ended up at the scene where Border Patrol agent Brian Terry was murdered last December . In early February 2011 , as the issue was heating up , the documents show Justice officials struggled for days over how to respond to Grassley . Repeated drafts were required as the issue rose for discussion among the deputy attorney general 's staff . At the last moment , Justice officials halted sending out letters to Grassley because of uncertainty over the facts of Fast and Furious , and over how forcefully to respond . Assistant Attorney General Ronald Weich was especially concerned about protecting the Justice Department position that details about ongoing investigations not be revealed . Other officials , notably in the deputy attorney general 's office , said it was crucial in this unusual and important situation to be candid and forthright to a key U.S. senator . Dennis Burke , the U.S. attorney for Arizona , defended the operation , and appears to have become exasperated at the Justice Department 's cautious response . `` Every version gets weaker . We will be apologizing to ( Grassley ) by tomorrow afternoon , '' he wrote . Burke and ATF headquarters officials insisted the charge that agents `` allowed the sale of weapons which were transported into Mexico is false . '' He also insisted the `` ATF makes every effort to interdict weapons that have been purchased illegally . '' When those claims , included in a February 4 letter to Grassley , later proved to be wrong , Assistant Attorney General Lanny Breuer and later Holder were forced to apologize to a Senate committee and to Grassley in particular . Burke resigned at the end of August , just days after testifying before a congressional committee . On Friday , Deputy Attorney General James Cole said the Justice Department `` now formally withdraws the February 4 letter . '' He said facts have come to light that indicate that the letter contains `` inaccuracies . '' Holder is expected to again express his `` regret '' for the misinformation before the Republican-controlled House Judiciary Committee . Breuer and Holder steadfastly maintain they did not know the assertions were wrong when the department sent Grassley the letter . Justice Department officials claim they were relying on information provided by ATF supervisors and their prosecutors in Phoenix . The document dump `` appears to raise ( even ) more questions '' for various officials involved in the program , said Beth Levine , a spokeswoman for Grassley . She made specific reference to `` disparaging e-mails '' from Burke about the Iowa senator . The former U.S. attorney `` personally apologized to Senator Grassley 's staff for the tone and the content of the e-mails '' after learning they 'd been released , according to Levine .
NEW : Grassley 's spokeswoman says the new documents raise more questions . Attorney General Eric Holder is to appear before a committee next week . Justice officials : Documents reflect internal debate about responding to allegations . The ATF is alleged to have let guns be taken illegally into Mexico .