The National Journal reported on Thursday that court papers released last week show that Libby was authorised to disclose classified information to news reporters by "his superiors" in an effort to counteract diplomat Joe Wilson's charge that the Bush administration twisted intelligence on Iraq's nuclear weapons to justify the 2003 invasion.

The magazine, citing attorneys familiar with the matter, reported on Thursday that Cheney was among those superiors referred to in a letter from prosecutor Patrick Fitzgerald to Libby's lawyers.

A lawyer for Cheney had no immediate comment.

Lewis "Scooter" Libby, Cheney's former chief of staff, faces perjury and other charges in the leak of the identity of Wilson's wife Valerie Plame, a move that effectively ended her career at the CIA.

Not guilty plea

Libby has pleaded not guilty to five counts of perjury, making false statements and obstruction of justice.

Cheney's name has surfaced in other court documents as well.

Cheney's name has reportedly
surfaced in court documents

According to an appeals-court decision made public last Friday, the vice-president informed Libby "in an off sort of curiosity sort of fashion" that Wilson's wife worked at the CIA one month before her identity was made public.

Both documents cite testimony Libby made to a grand jury.

Lawyers for Libby could not be reached for comment.

Scott McClellan, the White House spokesman, declined to comment.

"Our policy is we're not going to discuss this while there's an ongoing legal proceeding," McClellan said.