Congress ratcheted up the pressure today in the controversy surrounding the firing of several U.S. attorneys by sending subpoenas to two former high-ranking White House officials and a separate subpoena for documents to the White House chief of staff.
Under the subpoenas, former White House counsel Harriet Miers and Sara Taylor, a former aide to White House political adviser Karl Rove, will testify before Congress in mid-July about their roles in the attorney firings.
The action virtually assures a legal showdown between Democratic leaders in Congress and the Bush administration over revealing the White House's role in the controversy. Democrats claim that some of the federal prosecutors were fired for improper political reasons. The White House has resisted releasing information about its internal deliberations.
Taylor's lawyer, Neil Eggleston, said, "Ms. Taylor takes her responsibilities as a citizen very seriously, and she is hopeful the White House and the Congress are quickly able to work out an appropriate agreement on her cooperation with the Senate's proceedings."
Congressional leaders expressed mounting frustration with the White House on the issue.
"The bread crumbs in this investigation have always led to 1600 Pennsylvania," House Judiciary Committee Chairman John Conyers, D-Mich., said in a statement. "This investigation will not end until the White House complies with the demands of this subpoena in a timely and reasonable manner so that we may get to the bottom of this."
Should the White House choose to claim executive privilege over the testimony of the former administration aides, it would have to send a representative to the hearing. In a subpoena sent to White House Chief of Staff Joshua Bolten, Congress also asked for documents to be returned to the committee by June 28.
The subpoenas come on the heels of the Justice Department's release Tuesday night of more e-mails and internal documents.
Those latest e-mails and documents show more communication between the White House and the Justice Department on the firings of the eight federal prosecutors. Numerous e-mails show communications between Miers and Rove's deputies, as well as political aides Scott Jennings and Taylor.
Kyle Sampson, former chief of staff to Attorney General Alberto Gonzales, testified before the Senate Judiciary Committee about the matter earlier this spring.
Last week Fred Fielding, counsel to the president, wrote Conyers and Sen. Patrick Leahy, D-Vt., chairman of the Senate Judiciary Committee, to say the White House had "made efforts to resolve our differences" in a "mutually acceptable fashion" that would have avoided subpoenas.
Fielding reiterated his offer to have White House officials made available to Congress for informal interviews on the matter.
"We are not aware that any witness or document has provided any evidence supportive of the notion that any U.S. attorney was asked to resign in order to interfere with a pending or future criminal investigation," wrote Fielding.
Of Miers' and Taylor's subpoenas, White House spokesman Tony Fratto said, "We are aware of the Judiciary Committee's plans to issue subpoenas. We will respond appropriately."
"The committees can easily obtain the facts they want without a confrontation by simply accepting our offer for documents and interview," Fratto said, "but it's clear that Sen. Leahy and Rep. Conyers are more interested in drama than facts."
Leahy said in the statement accompanying the subpoenas that "by refusing to cooperate with congressional committees, the White House continues its pattern of confrontation over cooperation, and those who suffer most in this case are the public and the hard-working people at the Department of Justice."
"The White House cannot have it both ways — it cannot stonewall congressional investigations by refusing to provide documents and witnesses, while claiming nothing improper occurred," Leahy's statement continued.
The most notable e-mails released Tuesday concern the placement of Tim Griffin, a former aide of Rove's who replaced ousted U.S. attorney Bud Cummins in Arkansas.
Using her Republican National Committee e-mail account, Taylor e-mailed Sampson, then the chief of staff to Gonzales, on Feb. 7, 2007, about Cummins: "I normally don't like attacking our friends," she wrote, "but since Bud Cummins is talking to everyone — why don't we tell the deal on him?"
Almost a week later, Taylor e-mailed Sampson about a New York Times article that reported on the White House's involvement in the firings, and Deputy Attorney General Paul McNulty's testimony before the Senate Judiciary Committee that Cummins had done nothing wrong but was removed to make way for Griffin.
Taylor wrote to Sampson again Feb. 16, more than a week after McNulty had testified before the Senate Judiciary Committee. The message, with the subject line "McNulty strikes again," said, "Why would McNulty say this? This. has been so poorly, handled on the part O [sic] DOJ."
After Sampson said he would discuss the issue with her the following week, Taylor responded via her RNC e-mail account with apparent frustration, lashing out at Cummins:
"Tim was put in a horrible position; hung to dry w/ no heads up. You forced him to do what he did; this is not good for his long-term career. Bud runs a campaign and McNulty refuses to say Bud is lazy -- which is why we got rid of him in the first place," Taylor's e-mail said.
The message is titled "McNulty strikes again," and was sent the week before McNulty was due to testify before the House Judiciary Committee.
Taylor has since resigned from her White House post. Sampson stepped down in March amid the growing firestorm over the dismissals.
The lingering question is how a political operative at the White House knew a federal prosecutor had been labeled as "lazy."
Concerning the possible link to performance problems, Miers notes in a Jan, 16, 2007, e-mail to her deputy Bill Kelley, "I would really like to hear one precedent where we have been willing to discuss negatives about a person that is comparable to this situation. The individuals aren't saying anything public. Senators are. Then we are going to go out and say negative things about the people?"
Conyers said in a statement Tuesday, "These documents show that the White House played an integral role in the firings and their aftermath. This only underscores the need for White House cooperation with this investigation."
ABC News' Jon Garcia contributed to this report.