Libby is accused of lying about how and when he learned about Plame's identity in 2003 and told reporters about it.
The current charges in the CIA leak investigation stem from Special Counsel Patrick Fitzgerald's two-year investigation into whether Karl Rove, I. Lewis Libby or any other administration officials knowingly revealed the identity of CIA officer Valerie Plame or lied about their involvement to investigators.
Libby is accused of lying about how and when he learned about Plame's identity in 2003 and told reporters about it. The information on the officer was classified.
He is also accused of lying when he told Fitzgerald's investigators that he learned about Plame's status at the Central Intelligence Agency from Tim Russert of NBC television. He learned it from several government sources, including Cheney, the indictment says.
Any trial would dig into the secret deliberations of Bush and his team as they built the case for war against Iraq.
Bush ordered US troops to war in March 2003, saying deposed President Saddam Hussein's weapons of mass destruction program posed a grave and immediate threat to the United States. No such weapons were found. The US military death toll climbed past 2,000 this week.
On June 12, 2003, the indictment alleges, Libby heard directly from Cheney that Plame worked for the spy agency.
When the investigation began two years ago, a White House spokesman checked with Rove and Libby, then assured the public that neither was involved in leaking Plame's identity.
In the past month, it was revealed that Libby spoke to New York Times reporter Judith Miller, who says their conversations included Plame's status at the Central Intelligence Agency.
Rove's legal problems are in part the result of the fact that he initially failed to disclose to prosecutors a conversation in which he told Time magazine reporter Matt Cooper that Plame worked for the CIA. The president's top political adviser says the conversation slipped his mind.
Columnist Robert Novak revealed Plame's name and her CIA status on July 14, 2003. That was five days after Novak talked to Rove and eight days after Plame's husband, former ambassador Joseph Wilson, published an opinion article in the Times accusing the Bush administration of twisting intelligence to exaggerate the threat posed by Iraq.
Wilson and his supporters have contended that the leak of Plame's name, which ended her ability to work undercover for the CIA, was designed to discredit him and punish him for his criticism and to intimidate others inside the government critical of Bush's Iraq policies.