WASHINGTON– The prosecutor in the C.I.A. leak case on Monday advised Karl Rove, the senior White House adviser, that he would not be charged with any wrongdoing, effectively ending the nearly three-year criminal investigation that had at times focused intensely on Mr. Rove.

The decision by the prosecutor, Patrick J. Fitzgerald, announced in a letter to Mr. Rove’s lawyer, Robert D. Luskin, lifted a pall that had hung over Mr. Rove who testified on five occasions to a federal grand jury about his involvement in the disclosure of an intelligence officer’s identity.

In a statement, Mr. Luskin said, “On June 12, 2006, Special Counsel Patrick Fitzgerald formally advised us that he does not anticipate seeking charges against Karl Rove.”

Mr. Fitzgerald’s spokesman, Randall Samborn, said he would not comment on Mr. Rove’s status.

For months Mr. Fitzgerald’s investigation appeared to threaten Mr. Rove’s standing as Mr. Bush’s closest political adviser as the prosecutor riveted his focus on whether Mr. Rove tried to intentionally conceal a conversation he had with a Time magazine reporter in the week before the name of intelligence officer, Valerie Plame Wilson, became public. The decision not to pursue any charges removes a potential political stumbling block for a White House that is heading into a long and difficult election season for Republicans in Congress.

Mr. Fitzgerald’s decision should help the White House in what has been an unsuccessful effort to put the leak case behind it. Still ahead, however, is the trial of Vice President Dick Cheney’s former chief of staff, I. Lewis Libby Jr., on charges for perjury and obstruction of justice, and the prospect that Mr. Cheney could be called to testify in that case.

In his statement Mr. Luskin said he would not address other legal questions surrounding Mr. Fitzgerald’s decision. He added, “In deference to the pending case, we will not make any further public statements about the subject matter of the investigation. We believe that the Special Counsel’s decision should put an end to the baseless speculation about Mr. Rove’s conduct.”

But it was evident that Mr. Fitzgerald’s decision followed an exhaustive inquiry into Mr. Rove’s activities that had brought the political strategist dangerously close to possible charges. In October, when Mr. Libby was indicted, people close to Mr. Rove had suggested that his involvement in the case would soon be over; speculation about Mr. Rove’s legal situation flared again in April when he made his fifth appearance before the grand jury.

A series of meetings between Mr. Luskin and Mr. Fitzgerald and his team proved pivotal in dissuading the prosecutor from bringing charges. On one occasion Mr. Luskin himself became a witness in the case, giving sworn testimony that was beneficial to Mr. Rove.

As the case stands now, Mr. Fitzgerald has brought only one indictment against Mr. Libby. The prosecutor accused Mr. Libby of telling the grand jury that he learned of Ms. Wilson from reporters, when in reality, the prosecutor said he was told about her by Mr. Cheney and others in the government. Mr. Libby has pleaded not guilty in the case, which is scheduled to begin trial early next year.

Ms. Wilson is married to Joseph C. Wilson IV, the former ambassador who wrote in an Op-Ed column in the New York Times on July 6, 2003 that White House officials, including Mr. Bush, had exaggerated assertions that Iraq had sought to purchase nuclear fuel from Africa. Mr. Wilson wrote that such claims were “highly dubious.”

He said his conclusions were based on a trip he had made in early 2002 to Niger, a fact-finding mission that he said had been “instigated” by Mr. Cheney’s office.

It is now known that the column upset Mr. Cheney and that within his office it was viewed as an attack on the Vice President’s credibility, according to legal briefs filed in the Libby case by Mr. Fitzgerald. In his filings, Mr. Fitzgerald depicts Mr. Cheney as actively engaged in an effort with Mr. Libby to rebut Mr. Wilson’s assertions.

After the Wilson column was published, Mr. Cheney wrote notes on a copy asking whether Ms. Wilson played a role in sending her husband to Africa and whether the trip was a “junket.” At the same time, Mr. Fitzgerald has said, the vice president dispatched Mr. Libby to challenge Mr. Wilson in conversations with reporters.

It was during that effort, Mr. Fitzgerald has alleged, that Mr. Libby disclosed Ms. Wilson’s employment at the C.I.A. along with the possibility that it was she who sent him to Niger.

In Mr. Rove’s case, Mr. Fitzgerald centered his inquiry on why Mr. Rove did not admit early in the investigation that he had a conversation with Time magazine reporter Matthew Cooper about Ms. Wilson and whether Mr. Rove was forthcoming about the later discovery of an internal e-mail message that confirmed his conversation with Mr. Cooper, to whom Mr. Rove had mentioned the existence of the C.I.A. officer.

Mr. Rove told the grand jury that he forgot the conversation with Mr. Cooper and volunteered it to Mr. Fitzgerald as soon as he recalled it, when his memory was jogged by the e-mail to Stephen J. Hadley, then deputy national security adviser, in which Mr. Rove referred to his discussion with Mr. Cooper.

At the center of the inquiry involving Mr. Rove are the circumstances surrounding a July 11, 2003, telephone conversation between Mr. Rove and Mr. Cooper, who turned the interview to questions about the trip to Africa by Mr. Wilson.

In his testimony to the grand jury in February 2004, Mr. Rove did not disclose the conversation with Mr. Cooper, saying later that he had forgotten it among the hundreds of calls he received on a daily basis. But there was a record of the call in the form of Mr. Rove’s message to Mr. Hadley, the deputy national security adviser, which confirmed the conversation.

One lawyer with a client in the case said Mr. Fitzgerald was skeptical of Mr. Rove’s account because the message was not discovered until the fall of 2004 – a year after Mr. Rove first talked to investigators. It was at about the same time that Mr. Fitzgerald had begun to compel reporters to cooperate with his inquiry, among them Mr. Cooper. The prosecutors legal thrust at reporters, in effect, put White House aides like Mr. Rove on notice that any conversations might become known.

Associates of Mr. Rove said the e-mail message was turned over immediately after it was found at the White House. They said Mr. Rove never intended to withhold details of a conversation with a reporter from Mr. Fitzgerald, noting that Mr. Rove had signed a legal waiver to allow reporters to reveal to prosecutors their discussions with confidential sources. In addition, they said, Mr. Rove testified about his conversation with Mr. Cooper – long before Mr. Cooper did – acknowledging that it was possible that the subject of Mr. Wilson’s trip had come up.

It is now known that Mr. Fitzgerald and the grand jury have questioned Mr. Rove about two conversations with reporters. The first, which he admitted to investigators from the outset, took place on July 9, 2003, in a telephone call initiated by Robert D. Novak, the syndicated columnist. In a column about Mr. Wilson’s trip four days after the call to Mr. Rove, Mr. Novak disclosed the identity of Ms. Wilson, who was said by Mr. Novak to have had a role in arranging her husband’s trip. Mr. Novak identified her as Valerie Plame, Ms. Wilson’s maiden name.