Senate Democrats and a few Republicans have called for Mr. Rove to testify publicly about the dismissals.

“There is an issue of intrigue, and for better or worse, that surrounds Karl Rove,” said Senator Arlen Specter of Pennsylvania, the ranking Republican on the Senate Judiciary Committee. “It is in the president’s interest and the country’s interest to have it dispelled or verified, but let’s hear it from him.”

The White House, however, is offering only a private interview without a sworn oath.

Congressional Democrats said they were focusing on Mr. Rove in part because the administration appeared to have tried to hide his fingerprints. In a February 23 letter to Senate Democratic leaders that was approved by the White House counsel’s office, for example, the Justice Department said that no one in the White House had “lobbied” for any of the eight dismissals, and specifically denied that Mr. Rove had “any role” in the appointment of the protégé, J. Timothy Griffin, a former Bush campaign operative.

But the Justice Department officials who drafted the letter had corresponded with Mr. Rove’s staff just weeks earlier about how to get the nomination done. On Wednesday night, a department official apologized for inaccuracies in the letter.

White House officials said Mr. Rove was just one voice in the approval of federal prosecutors, whose selection is traditionally guided by the recommendations of senior members of the president’s party in their states.

“Our job is to find qualified nominees who can win confirmation and be good public servants,” said Dana Perino, a White House spokeswoman. After the United States attorneys are confirmed, she said, Mr. Rove and others at the White House show “wide deference” to the Justice Department about specific cases.

Some Republicans say they always understood that Mr. Rove had a say in prosecutor appointments. “I basically felt when I was talking to Karl I was talking to the president,” said former Senator Peter G. Fitzgerald, an Illinois Republican.