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WASHINGTON (CNN) -- Former Deputy Secretary of State Richard Armitage was the source who revealed the identity of CIA officer Valerie Plame to syndicated columnist Robert Novak in 2003, touching off a federal investigation, two sources familiar with Armitage's role tell CNN.
The sources said Armitage revealed Plame's role at the CIA almost inadvertently in a casual conversation with Novak, and it is not clear if he knew her identity was classified at the time.
Armitage was not indicted by the federal grand jury that investigated the disclosure of Plame's name to Novak and other journalists. Deliberately revealing the identify of a CIA operative can be a crime.
The revelation that Armitage was the source of Novak's column is somewhat anticlimactic for Bush administration critics who had used the story as a weapon in Washington's partisan battles.
During the run-up to the Iraq war in 2003, Armitage was viewed as one of the more skeptical voices in the administration about the need to depose Saddam Hussein by force.
In a July 14, 2003, column, Novak noted that Plame was a CIA operative, citing two senior administration officials. The column was primarily about Plame's husband, Joe Wilson, a former career diplomat and critic of the intelligence underlying the invasion of Iraq.
Wilson and some Democrats contend Plame's identity was released by the White House to retaliate against her husband for writing a July 2003 column in The New York Times that questioned the administration's use of prewar intelligence on Iraq. (Full story)
Last month, Plame and Wilson filed a civil lawsuit alleging a conspiracy that "was motivated by an invidiously discriminatory animus towards those who had publicly criticized the administration's stated justifications for going to war with Iraq" and culminated with the disclosure that Plame worked at the CIA. This revelation destroyed Plame's career with the agency, according to the suit.
The scenario described by the sources familiar with Armitage's role, however, appears to contradict those arguments.
But the Wilsons' attorney, Melanie Sloan of Citizens for Responsibility and Ethics in Washington, said the revelation that Armitage was the original source for the leak did not undercut the charge that Vice President Dick Cheney, Cheney's former chief of staff I. Lewis "Scooter" Libby and White House adviser Karl Rove acted to retaliate against Wilson by engaging in a "whispering campaign" about his wife.
The couple plans to proceed with the lawsuit, Sloan said.
"Mr. Armitage's conduct does not change the facts of what Libby, Cheney and Rove did," Sloan told CNN. "The case is about the abuse of government power."
Novak has never revealed the original source of the information about Plame. However, he has said that Rove confirmed the information and was the second source cited in the column.
Novak has said he would not reveal the identity of the original source unless the source came forward. However, he said the special counsel in the CIA leak investigation, Patrick Fitzgerald, learned who the source was independently.
Fitzgerald has said he does not plan to bring any charges against Novak's original source.
Calls to Armitage for comment were not returned Tuesday.
The Armitage connection to the Novak column is also outlined in a new book titled "Hubris" by Michael Isikoff and David Korn.
In the book, Armitage is quoted as telling former Assistant Secretary of State Carl Ford that "I'm afraid I may be the guy that caused this whole thing."
Calls to Ford for comment also were not returned Tuesday.
In September 2003, Fitzgerald, the U.S. attorney in Chicago, Illinois, was appointed as a special counsel to investigate whether any laws were broken with the disclosure.
No one has been indicted for leaking Plame's identity, but Libby has been charged with perjury, obstruction of justice and lying to investigators for allegedly giving false information about his discussions with journalists about Plame.
Libby has denied any wrongdoing and pleaded not guilty.
Fitzgerald notified Rove that he wouldn't be charged in the case, Rove's attorney, Robert Luskin, said in June.
As part of his investigation, Fitzgerald subpoenaed then-New York Times reporter Judith Miller and then-Time magazine reporter Matthew Cooper. In 2005, Miller spent nearly 12 weeks in jail after she refused to testify to identify her source to Fitzgerald. (View a timeline of the CIA leak case)
Miller was released after her source, Libby, called her and personally waived their confidentially agreement.
Armitage, 65, was No. 2 at the State Department under former Secretary of State Colin Powell from 2001 to 2005.
He left his post after Powell resigned at the beginning of Bush's second term.
CNN's John King and Brian Todd contributed to this report.
Former Deputy Secretary of State Richard Armitage has been revealed as the original source of the information about Valerie Plame that made its way into Robert Novak's column about the Niger affair.  According to sources, Armitage discussed it casually and it is not clear whether he had knowledge of her classified status.  

Plame and her husband Joseph Wilson have filed a civil lawsuit alleging that the administration intentionally used the leak to retaliate against him for his criticism of the war on Iraq.

According to ABC News, when Armitage realized he was the source of the leak early on in the affair, he informed the FBI of it.