CHICAGO --Another stunning development in the corruption trial of political fundraiser Tony Rezko: prosecutors say a witness is ready to testify that a powerful friend of Rezko worked with White House political director Karl Rove to try and fire U.S. attorney Patrick Fitzgerald.Could Illinois Republicans and Democrats work hand-in-hand to get rid of a U.S. attorney who they believed was a bit too enthusiastic about ending corruption in state government? That's the story being told by a freshly minted government witness who the feds are trying to put to work immediately in the Tony Rezko trial. When Rezko arrived at the courthouse Wednesday he got the official word that the government was trying to strengthen its case in the middle of the Democratic party fundraiser's corruption trial. Federal prosecutors asked Judge Amy St. Eve if they could add to their witness list the name of 56-year-old Ali Ata, the former Illinois finance authority director. Ata, a codefendant with Rezko in an unrelated business fraud case, pleaded guilty Tuesday and promised to help the government in return for a lesser sentence. Assistant U.S. attorney Carrie Hamilton told Judge St. Eve that, a few months after the FBI began investigating Rezko in 2004, Ata "had conversations with Mr. Rezko about the fact that Mr. Kjellander (Robert, an Illinois Republican insider) was working with Karl Rove (then White House chief-of-staff) to have Mr. Fitzgerald (Chicago's U.S. attorney) removed....so that someone else can come in to the U.S. attorneys office and individuals who have been cooperating in this investigation will be dealt with differently." Former federal prosecutor Ron Safer said for the judge to allow such a witness to be added at mid-trial would be unusual. "Is it fair to the government to deprive it of evidence against a defendant in a criminal case?" Safer asked. Defense attorney Joseph Duffy opposes testimony by Ata, arguing it would not be relevant to the charges in Rezko's now seven-week-old trial. In his plea agreement revealed Tuesday, Ata claimed to have been appointed to his job at the IFA in return for campaign contributions to "public official A," with whom he allegedly met in Rezko's office on Chicago's near northwest side. A spokeswoman for Governor Rod Blagojevich has denied her boss is "public official a," e-mailing Tuesday, "We don't endorse or allow the decisions of state government to be based on campaign contributions." The judge has not ruled yet on whether Ata will be allowed to testify. Meanwhile, Karl Rove -- now a private consultant in Washington -- issued a statement through his attorney saying he did not recall any such conversations and denied that he ever sought Patrick Fitzgerald's firing. Kjellander said he never talked to Karl Rove about firing Patrick Fitzgerald and never told anyone he wanted to do so.