A former key White House official, Lewis Libby, has been found guilty of obstruction of justice and perjury.
Lewis "Scooter" Libby was a key figure in the White House
Libby, ex-chief of staff to Vice-President Dick Cheney, faces a prison term of up to 25 years. He will be sentenced in June.
He was accused of lying to the FBI and a grand jury over revelations about CIA agent Valerie Plame's identity.
Libby's lawyer said he was "very disappointed" at the verdict, and would ask for a new trial, or would appeal.
In a statement shortly after the verdict was announced, Mr Cheney expressed his deep disappointment, saying he was "saddened" for Libby's family.
Libby, who goes by the nickname "Scooter", was found guilty on four out of five counts. He was acquitted on one count of lying to the FBI.
Critics claimed the White House had deliberately leaked Ms Plame's identity to ruin her career. Her husband, former ambassador Joseph Wilson, had publicly cast doubt on the Bush administration's case for going to war in Iraq.
It can be a crime to reveal the identity of an undercover CIA agent.
The alleged cover-up, rather than the leak itself, was the subject of the trial.
Libby told FBI investigators and a grand jury investigating the leak of Ms Plame's name, that he had learned of her identity as a CIA agent from reporters.
However, several people testified that he discussed her identity before the date he said he learned of it.
It was alleged Valerie Plame was targeted because of her husband
"He claims he forgot nine conversations with eight people over a four-week period," prosecution lawyer Peter Zeidenberg said in his closing statement.
The defence maintained that Libby's false statements were the results of honest lapses in memory by a man tasked with extraordinary responsibility.
"He was bombarded with a blizzard of information. Those briefings would make your toes curl," defence lawyer Theodore Wells said.
The defence also argued that Libby was a scapegoat for the misdeeds of other White House players, like President Bush's political strategist Karl Rove.
After the verdict, and standing beside his client, who remains free until sentencing, Mr Wells said: "We have every confidence that ultimately Mr Libby will be vindicated.
"We believe he is totally innocent, and did not do anything wrong."
Prosecutor Patrick Fitzgerald said he was "gratified" by the verdict, but that it was "sad" that "we had a high-level official... who obstructed justice and lied under oath".
US President George W Bush "said that he respected the jury's verdict. He said he was saddened for Scooter Libby and his family," said White House spokeswoman Dana Perino.
But Senate majority leader Harry Reid said: "I welcome the jury's verdict. It's about time someone in the Bush administration has been held accountable for the campaign to manipulate intelligence and discredit war critics."
A member of the jury, Denis Collins, said although jurors decided Libby was guilty they also had a "tremendous amount of sympathy" for him, and thought he might just be "the fall guy".
"Where's Rove?" he asked, referring to Mr Bush's top aide.