A report in Tuesday's New York Times says the chief of staff to Vice President Dick Cheney learned about the identity of a covert CIA officer during a discussion with the vice president more than two years ago.
The Times says Lewis Libby discussed covert officer Valerie Plame with Mr. Cheney during a meeting several weeks before her identity was made public in a newspaper column.
White House spokesman Scott McClellan did not answer questions about the leak investigation Tuesday, saying Mr. Cheney is doing a "great job" as vice president.
Mr. Libby has emerged as a key figure in the investigation of the disclosure of Valerie Plame's identity to reporters. Disclosing the identity of an undercover intelligence agent is a violation of U.S. law.
Ms. Plame is married to former Ambassador Joseph Wilson, who criticized the Bush administration's reasons for invading Iraq.
The Times says Mr. Libby previously testified that he learned of Ms. Plame's identity from reporters.
The special counsel in the leak investigation, Patrick Fitzgerald, is expected to decide by the end of this week whether to seek criminal indictments in the case.
Some information for this report provided by AFP and AP.