WASHINGTON (Reuters) - U.S. President Donald Trump on Friday pardoned former George W. Bush administration official Lewis “Scooter” Libby, who years ago was convicted of lying in an investigation of the unmasking of a CIA agent.

Democrats immediately criticized the president’s move, drawing an arc running from the Iraq war to today and linking the Libby pardon to Trump’s bitter feud with James Comey, who Trump fired as FBI director last year, and to a widening investigation of possible links between the Trump campaign and Russian meddling in the 2016 presidential election.

The Libby pardon came just hours after Trump’s morning Twitter attack against Comey. The president called the ex-FBI chief a “weak and untruthful slime ball.”

Excerpts of Comey’s new book due out Tuesday, “A Higher Loyalty: Truth, Lies and Leadership,” slam Trump, calling him “unethical, and untethered to truth and institutional values.”

Before heading the Federal Bureau of Investigation, Comey was deputy attorney general during the Bush administration. During that time, he appointed a special counsel to prosecute a high-profile case that led to Libby’s guilty verdict in 2007.

“I don’t know Mr. Libby,” Trump said in a White House statement, “but for years I have heard that he has been treated unfairly. Hopefully, this full pardon will help rectify a very sad portion of his life.”

Libby could not immediately be reached for comment.

Conservative Republicans had sought a pardon for Libby for years after former Vice President Dick Cheney was unable to persuade Bush to grant one late in his presidency. Bush did, however, commute Libby’s 2-1/2-year prison sentence.

Libby, chief of staff to Cheney during the run-up and early years of the Iraq war, was found guilty in 2007 of lying and obstructing an investigation into who blew the cover of CIA officer Valerie Plame. Her husband Joseph Wilson, a former career U.S. diplomat, had criticized the Iraq war.

‘SIMPLY FALSE’

“President Donald Trump has granted a pardon to I. Lewis ‘Scooter’ Libby on the basis that he was ‘treated unfairly.’ That is simply false. Libby was convicted of obstruction of justice and perjury in a fair trial,” Plame said in a statement.

House of Representatives Democratic leader Nancy Pelosi said in a statement, “This pardon sends a troubling signal to the president’s allies that obstructing justice will be rewarded.”

Representative Adam Schiff, the top Democrat on the House Intelligence Committee, said the Libby pardon was Trump’s way “of sending a message to those implicated in the Russia investigation: You have my back and I’ll have yours.”

FILE PHOTO: Lewis "Scooter" Libby listens as his attorney speaks to the media at the U.S. Federal Courthouse in Washington March 6, 2007. REUTERS/Jim Bourg/Files

The Libby pardon coincided with the arrival in the White House of John Bolton as Trump’s new national security adviser. Bolton was a key Bush administration advocate, along with Cheney and Libby, of the 2003 U.S. invasion of Iraq.

“I am grateful today that President Trump righted this wrong by issuing a full pardon to Scooter,” Cheney said in a statement.

Bush spokesman Freddy Ford said, “President Bush is pleased for Scooter and his family.”

White House spokeswoman Sarah Sanders, in a briefing with reporters, said on Friday that the pardon had nothing to do with Trump’s views on Mueller’s investigation.

Trump has been attacking the FBI amid the investigation of his 2016 presidential campaign for possible links to Russian meddling in the 2016 election.

Paul Manafort, Trump’s former campaign chairman, and a key Manafort associate are among those who have been indicted in the Russian meddling probe run by Special Counsel Robert Mueller.

White House aides said earlier this week that Trump was fuming over FBI raids related to the investigation on Monday of the office and home of his personal attorney, Michael Cohen.

Trump has repeatedly called Mueller’s probe a “witch hunt” and he and Russia have both denied any wrongdoing.

It was the second high-profile pardon of Trump’s tenure. Last year, he pardoned Joe Arpaio, a former Arizona sheriff who campaigned for Trump, less than a month after he was convicted of criminal contempt in a case involving racial profiling.