US:US vice-president Dick Cheney will be called as a defence witness in the CIA leak case of his former chief of staff, Lewis "Scooter" Libby, next year, according to Mr Libby's lawyers.
Mr Cheney's staff declined to say if he would become the first serving vice-president ever to testify in court, but promised that the White House would co-operate with the court.
"We've co-operated fully in this matter and will continue to do so. In fairness to the parties involved and as we've stated previously, we're not going to comment further on a legal proceeding," spokeswoman LeAnn McBride said in a statement.
Special counsel Patrick Fitzgerald, who has been investigating the leaking of CIA agent Valerie Plame's identity, said he did not expect Mr Cheney to resist being called, stating that he "is not aware of any government witness who is intending to assert a blanket privilege, and the government does not otherwise anticipate any of its witnesses moving to quash or limit trial subpoenas".
Conservative commentator Robert Novak revealed Ms Plame's identity as a CIA agent after her husband, former ambassador Joseph Wilson, publicly questioned intelligence claims the Bush administration made in the run-up to the Iraq war.
Libby is charged with lying to investigators and a grand jury about his conversations with journalists regarding Ms Plame and his trial is expected to start in mid-January. Mr Fitzgerald has asserted that it was Mr Cheney who revealed Ms Plame's job to Mr Libby.
Neither Mr Libby nor Mr Fitzgerald has asserted that the vice-president directed Mr Libby to leak the CIA agent's name to reporters, but White House documents presented to the court show Mr Cheney was concerned with Mr Wilson's criticism.