U.S. Deputy Attorney General Rod Rosenstein was so upset with the White House for pinning the firing of FBI Director James Comey on him Wednesday that he was on the verge of resigning, an administration source told ABC News.

After Comey’s firing Tuesday night, White House officials said the president acted on the recommendation of Rosenstein.

Deputy press secretary Sarah Huckabee Sanders said on “Good Morning America” today that she was “not aware” of Rosenstein’s contemplating his resignation.

In his letter written to staff and friends after he was fired, Comey said he was not going to dwell on how his firing was handled.

“I’m not going to spend time on the decision or the way it was executed. I hope you won’t either. It is done,” Comey wrote. “In times of turbulence, the American people should see the FBI as a rock of competence, honesty and independence.”

In a memo delivered Tuesday afternoon to President Trump, Rosenstein wrote that Comey inflicted “substantial damage” to the FBI’s “reputation and credibility.”

The White House initially said Rosenstein’s recommendation was the reason Trump chose to fire Comey.

“When he brought the recommendation to the president that the director of the FBI should be removed, President Trump provided the kind of strong and decisive leadership the American people have become to be accustomed from him,” Vice President Mike Pence said Wednesday on Capitol Hill.

Press secretary Sean Spicer pointed the finger at the Justice Department when asked by ABC News late Tuesday night who ordered the review of Comey.

But Sanders said during Wednesday’s White House press briefing that Trump “made the decision for the final decision to move forward with it was yesterday. But I know that he’s been contemplating it for a while.”

When asked whether Comey’s firing was a result of Rosenstein’s memo, Sanders said, “That was, I think, the final piece that moved the president to make that quick and decisive action yesterday.”

Despite their having been critical of Comey for his handling of the Hillary Clinton email investigation, Democrats argue that the firing of Comey, who was overseeing the Russia investigation, is an abuse of presidential power.

“The reality is his team is the subject of an investigation,” Adam Schiff, the ranking member of the House Intelligence Committee, said in an interview with CNN Wednesday. “None of us know where that investigation is going to lead and that’s a very apparent conflict of interest for the president.”

In his letter to Comey telling him he was “terminated,” Trump made a point of raising the FBI’s Russia probe.

“I greatly appreciate you informing me, on three separate occasions, that I’m not under investigation,” Trump wrote.

Associates of Comey told ABC news they are highly skeptical that Comey ever would have told the president that he was not under investigation.

They say it’s possible that was the president’s understanding but Comey would never have cleared anybody while the investigation is still under way, the associates said, adding that it would have been highly inappropriate for Comey to do so.

(Source: ABC News)