Cheney aide resigns over CIA leak
Lewis Libby has been an influential figure in the White House
A top aide to the US vice-president has resigned after being charged with perjury over an investigation into the unmasking of a covert CIA agent.
Lewis Libby, chief-of-staff to Dick Cheney, was also charged with obstruction of justice and making false statements to the federal grand jury.
Presidential adviser Karl Rove appears to have escaped immediate indictment.
The identity of CIA agent Valerie Plame - whose husband criticised the Iraq war - was leaked to a US reporter in 2003.
Revealing the identity of a covert agent is a federal offence.
Special prosecutor Patrick Fitzgerald has accused Mr Libby of lying about how and when he learned and disclosed to reporters classified information about Ms Plame.
LEWIS LIBBY INDICTMENT
Two charges of perjury
Two counts of making a false statement
One charge of obstruction of justice
Indictment in full (110kb)
If found guilty on all five counts in the indictment, the 55-year-old faces a maximum of 30 years in prison and a $1.25m (£705,000) fine for each charge.
Mr Fitzgerald is to hold a news conference on Friday giving details of his investigation.
In a statement released with the indictment, Mr Fitzgerald said: "When citizens testify before grand juries, they are required to tell the truth.
"The requirement to tell the truth applies equally to all citizens including persons who hold high positions in government."
No other official has been charged, although Mr Rove has been told he remains under investigation by the grand jury.
'Presumed innocent'
White House spokesman Scott McClellan said Mr Libby's resignation had been accepted and he was no longer at the White House.
Mr Cheney released a statement saying Mr Libby would fight the charges and must be presumed innocent until found guilty by a jury.
HAVE YOUR SAY
As an American, I am saddened by the state of our nation
Nate, Minneapolis, USA
Send us your views
He said he had accepted his former chief-of-staff's resignation "with regret".
The BBC's Washington correspondent, Matt Frei, says the announcement is mixed news for the president.
He can take some comfort in the fact that his own right-hand man, Karl Rove, has for now escaped prosecution - even if he remains under investigation for the next six months.
Ms Plame's identity was leaked after her husband, diplomat Joseph Wilson, accused the Bush administration of manipulating intelligence to support military action against Iraq.
Mr Wilson says it was done to undermine his credibility. Others have raised the possibility that it was a form of payback for her husband's criticism.