Vice President Cheney's chief of staff, I. Lewis "Scooter" Libby, was indicted today by a federal grand jury after a nearly two-year investigation into the leak of a CIA agent's identity.

Capping a week of political turmoil in Washington, Libby promptly resigned and left the White House. He expressed confidence that eventually he would be "totally exonerated," and both Cheney and President Bush praised his talent and dedication. "Obviously, today is a sad day for me and my family," Libby said in a statement.

The grand jury did not return an indictment against another top administration official who was caught up in the probe: Karl Rove, President Bush's top political strategist. But the special counsel in the case, Patrick J. Fitzgerald, said the investigation is "not over" and that another grand jury would be kept open in case prosecutors decide to press other charges.

Libby, 55, was indicted on charges of perjury, obstruction of justice and making false statements. The five-count indictment charges that he lied to FBI agents and to the federal grand jury about how and when he learned classified information about the employment of a CIA agent, Valerie Plame, and disclosed that information to three journalists. If convicted on all counts, Libby faces up to 30 years in prison and a $1.25 million fine.

In brief remarks before flying to Camp David for the weekend, Bush said he had accepted the resignation and praised Libby as an aide who "worked tirelessly on behalf of the American people and sacrificed much in the service to this country." He called the investigation "serious" and said the process now moves to a new phase, leading to a trial.

"While we are all saddened by today's news, we remain wholly focused on the many issues and opportunities facing this country," Bush said. "I got a job to do, and so do the people who work in the White House." He did not take any questions from reporters.

Cheney said in a statement that he accepted Libby's resignation "with deep regret." He called his aide "one of the most capable and talented individuals I have ever known." Cheney added that "it would be inappropriate for me to comment on the charges or on any facts relating to the proceeding."

The indictment was handed up today as the grand jury's term expired. Although no indictment was announced for Rove, 54, the White House deputy chief of staff, today's proceedings did not remove him from legal jeopardy, since the investigation is continuing.

An attorney for Rove, Robert Luskin, said in a statement this morning, "The Special Counsel has advised Mr. Rove that he has made no decision about whether or not to bring charges and that Mr. Rove's status has not changed. Mr. Rove will continue to cooperate fully with the Special Counsel's efforts to complete the investigation. We are confident that when the Special Counsel finishes his work, he will conclude that Mr. Rove has done nothing wrong."

Rove provided new information to Fitzgerald during eleventh-hour negotiations that "gave Fitzgerald pause" about charging Bush's senior strategist, said a source close to Rove. "The prosecutor has to resolve those issues before he decides what to do."

"We're not quite done," Fitzgerald said in an hour-long news conference this afternoon. But he refused to comment on whether anyone beside Libby would be charged in the case or whether additional charges against Libby would be sought.

"I will not end the investigation until I can look anyone in the eye and tell them we have carried out our responsibility sufficiently," Fitzgerald said.

Asked about what a reporter described as "Republican talking points" minimizing the significance of today's charges, the prosecutor said lying under oath "is a very, very serious matter" and a "serious breach of the public trust."

He said, "We didn't get the straight story, and we had to take action."

Fitzgerald said that contrary to what Libby told the FBI and the grand jury, he had held at least seven discussions with government officials regarding the CIA agent before the day when he claimed to have learned about her from Tim Russert of NBC News. "And in fact, when he spoke to Mr. Russert, they never discussed it," Fitzgerald said.

"At the end of the day, what appears is that Mr. Libby's story that he was at the tail end of a chain of phone calls, passing on from one reporter what he heard from another, was not true," the special counsel said. "It was false. He was at the beginning of the chain of phone calls, the first official to disclose this information outside the government to a reporter. And then he lied about it afterwards, under oath and repeatedly."

The indictment contains one count of obstruction of justice, two counts of perjury and two counts of making false statements. The charges involve testimony that Libby gave to the grand jury and other statements he made regarding his conversations with three journalists: Judith Miller of the New York Times, Matthew Cooper of Time magazine and Russert.

Libby is to be arraigned at a later date. The case has been assigned to U.S. District Judge Reggie B. Walton, an appointee of President Bush.

A press release issued by the special counsel's office said that before Plame's name appeared in the press in July 2003, her CIA employment was classified and her affiliation with the agency "was not common knowledge outside the intelligence community." It said that disclosing such information "has the potential to damage the national security" by preventing the person from operating covertly in the future, compromising intelligence-gathering and endangering CIA employees and those who deal with them.

However, the indictment does not charge Libby with the original alleged offense that the grand jury set out to investigate: illegally revealing the identity of a covert agent in violation of a 1982 federal law.

The presentation of the indictment lasted less than five minutes from the time U.S. Magistrate Judge Deborah A. Robinson entered courtroom No. 4 on the second floor of the E. Barrett Prettyman Federal Courthouse at 12:35 p.m. Fitzgerald and 10 members of his legal team, as well as the jury forewoman, had come to the courtroom about 15 minutes earlier, taking seats around a large wooden table near the center of the room and talking quietly among themselves. The rest of the grand jury entered a few minutes later. Neither Libby nor any of his attorneys was in the courtroom.

The grand jury included nine black women, four white women, three black men, two white men and a Hispanic man. Most appeared to be middle-aged or older, and all wore blank faces or serious expressions at today's proceeding. They sat quietly and did not speak to each other before the indictment was announced.

As tension mounted ahead of the indictment, the White House adopted a business-as-usual approach. Bush traveled to Norfolk, Va., today to deliver a speech on the war on terrorism, and Cheney was in Georgia to attend several political events.

The investigation by the federal grand jury in Washington was originally launched to determine whether anyone illegally leaked the name of Plame, a covert CIA agent, in an effort to discredit her husband, former ambassador Joseph C. Wilson IV, in retaliation for his criticism of the war in Iraq. Wilson began criticizing the war and the Bush administration after a 2002 trip he took at the behest of the CIA to the African country of Niger to look into reports that Iraq was seeking materials to build nuclear weapons.

In a statement read by his lawyer this afternoon, Wilson said, "Whatever the final outcome of the investigation and the prosecution, I continue to believe that revealing my wife Valerie's secret CIA identity was very wrong and harmful to our nation, and I feel that my family was attacked for my speaking the truth about the events that led our country to war."

But he said the indictment was no reason to celebrate. "Today is a sad day for America," Wilson said. "When an indictment is delivered at the front door of the White House, the office of the president is defiled. No citizen can take pleasure from that."

The indictment charges that Libby began acquiring information about Wilson's trip in May 2003 after a New York Times columnist disputed the accuracy of a Bush statement in his State of the Union address. The column said a former ambassador, who was not named, found the statement to be false.

According to the indictment, Libby learned Plame's identity from a senior State Department official in June 2003 and was told by Cheney that she worked in the CIA's Counterproliferation Division.

The two key subjects of the inquiry -- Rove and Libby -- have acknowledged talking about Plame to reporters, but they have denied leaking her name or committing other wrongdoing.

Libby testified that he did not identify Plame by name to reporters or discuss her covert status with them. But Miller of the New York Times has testified that she believed she first learned of Plame's CIA job from Libby, when the two spoke on June 23, 2003. Miller said she and Libby discussed Plame again in a meeting on July 8, 2003, and in a phone conversation a few days later, on July 12. She has said she first learned Plame's name from someone other than Libby but does not recall who it was.

The reported effort to discredit Wilson was rooted in a clash between the White House -- notably Cheney -- and the intelligence bureaucracy in the CIA and State Department over the war in Iraq. Grand jury testimony that has been disclosed suggests that Bush administration officials suspected the CIA of trying to shift blame for prewar intelligence failures to the White House.

The vice president played a central role in assembling the case for invading Iraq and repeatedly pressed for intelligence that would bolster his arguments. Ironically, it was a question from Cheney during an intelligence briefing that initiated the chain of events that led to the grand jury investigation. He had received a military intelligence report alleging that Iraq was seeking uranium from Niger and asked what the CIA knew about it.

As a result, Wilson was dispatched in February 2002 to look into claims that Iraqi President Saddam Hussein had attempted to buy uranium yellowcake from Niger for use in developing nuclear weapons. Wilson has said he found no evidence of any such effort and reported that the claims were false.

Nevertheless, President Bush said in his January 2003 State of the Union address that the British government had learned Hussein "recently sought significant quantities of uranium from Africa."

Two months later, Bush ordered U.S. troops into Iraq to depose Hussein and eliminate a purported threat to the United States from Iraqi "weapons of mass destruction." No such weapons were found, nor was there evidence that the Hussein regime had reconstituted a nuclear weapons program.

In an opinion piece published in the July 6, 2003, New York Times, Wilson criticized Bush's State of the Union statement. Wilson wrote that if his findings in Niger were ignored because they did not fit the administration's "preconceptions about Iraq," then a case could be made "that we went to war under false pretenses." He said some intelligence related to Iraq's nuclear program was "twisted to exaggerate the Iraqi threat."

On July 14, conservative political commentator Robert D. Novak wrote a syndicated column that called Wilson's African mission into question, suggesting the trip was instigated by Wilson's wife and did not have high-level backing. Novak named Plame as "an Agency operative on weapons of mass destruction" and said "two senior administration officials" had told him she had suggested sending her husband on the Niger trip.

Wilson subsequently complained that the Bush administration had compromised his wife's CIA career in retribution against him.

The CIA then asked the Justice Department to investigate the leak. Fitzgerald, a hard-charging U.S. attorney in Chicago, was appointed special counsel for the probe in late December 2003. His charge was to determine whether anyone involved in the leak violated federal law, including the Intelligence Identities Protection Act of 1982. The act makes it a felony, punishable by up to 10 years in prison, for a person with access to classified information to intentionally disclose the identity of a covert agent to anyone not authorized to receive classified information.

During the investigation, Fitzgerald sought grand jury testimony from several journalists who had spoken with administration officials about Plame, and he came down hard on those who refused to cooperate.

The federal judge in the case, Thomas F. Hogan, ordered the New York Times's Miller held for contempt for refusing to identify a confidential source, and she spent 85 days in jail in Alexandria, Va., before agreeing to testify about conversations with Libby. Although she did not write an article about the case, Miller interviewed Libby about the Plame matter and promised him anonymity. Miller said she agreed to testify when Libby specifically and personally released her from the confidentiality pledge.

Among those interviewed by Fitzgerald in the case have been Bush, Cheney and several of their top aides and advisers.

Washington Post staff writer Jim VandeHei contributed to this article.