U.S. President George W. Bush acknowledged for the first time that someone from his administration leaked the name of an undercover CIA agent to a reporter, but said Thursday he hoped the issue had run its course.

During a White House news conference, Bush was asked about his controversial decision to commute the 30-month prison sentence of I. Lewis (Scooter) Libby, the former chief of staff to Vice-President Dick Cheney.

Libby had been convicted of lying and obstruction of justice in the CIA leak case involving undercover CIA official Valerie Plame. Critics of the administration accused the White House of leaking her name because her husband, Joseph Wilson, was a vocal anti-war critic.

"I'm aware of the fact that perhaps somebody in the administration did disclose the name of that person," Bush said.

"I've often thought about what would have happened if that person had come forth and said, 'I did it.' Would we have had this endless hours of investigation and a lot of money being spent on this matter?

No one was charged with the leak itself. It was later revealed that deputy secretary of state Richard Armitage leaked the name to columnist Robert Novak for his 2003 newspaper article which outed Plame.

Novak said he also called White House political adviser Karl Rove, who also confirmed Plame's identity.

Former White House press secretary Ari Fleischer also admitted telling reporters about her.

Bush had initially threatened to fire anyone who had publicly disclosed Plame's identity.

"It has been a tough issue for a lot of people in the White House, and it's run its course, and now we're going to move on," Bush said.

With files from the Associated Press