Trump pardons ex-Cheney aide convicted of lying over CIA name leak

US President Donald Trump pardoned a former White House aide convicted of lying to the FBI in connection with the leak of a CIA operative's identity -- a move seen by critics as a message to witnesses in the current Russia probe.

"I don't know Mr. Libby," Trump said of vice president Dick Cheney's former chief of staff Lewis "Scooter" Libby. "But for years I have heard that he has been treated unfairly," Trump added. "Hopefully, this full pardon will help rectify a very sad portion of his life." Libby was handed a 30-month prison sentence for perjury, obstruction of justice and making false statements to investigators in 2007.

His sentence was commuted by former president George W Bush, who declined however to issue a pardon -- sparking a rift between him and Cheney.

The affair dates back to July 2003 when the name of CIA agent Valerie Plame, the wife of a diplomat who had accused the Bush administration of exaggerating the threat posed by Iraq, was leaked to the press.

Libby was not accused of blowing Plame's cover, but of lying during the subsequent inquiry.

Democrats were quick to criticise the decision -- and its possible repercussions on the probe led by Special Counsel Robert Mueller into Russian interference in the 2016 election and allegations of collusion with the Trump campaign, as well as possible obstruction of justice.

"President Trump's pardon of Scooter Libby makes clear his contempt for the rule of law," said leading congresswoman Nancy Pelosi.

"This pardon sends a troubling signal to the president's allies that obstructing justice will be rewarded," she added. "The suggestion that those who lie under oath may be rewarded with pardons poses a threat to the integrity of the Special Counsel investigation, and to our democracy. Neither the president nor his allies are above the law."