US Deputy Attorney General Rod Rosenstein arrives on Capitol Hill in Washington, Thursday, May 18, 2017, for a closed-door meeting with Senators a day after appointing former FBI director Robert Mueller to oversee the investigation into possible ties between Russian Federation and US President Donald Trump's campaign.
Trump clearly knew what he wanted to say as he took a few questions at a news briefing with visiting Colombian President Juan Manuel Santos.
"We have a very divided country because of that and many other things", Trump said.
But Mr Trump said the appointment of a special prosecutor to probe his campaign's ties with Russian Federation "hurts our country terribly".
While Trump questioned the legitimacy of the investigation, it has thrown the administration off track and consumed its political capital.
Appointing a special counsel could briefly calm the waters, temporarily cooling the partisan tensions.
"There has been no collusion between certainly myself and the campaign - but I can always speak for myself - and the Russians: zero", Trump said.
He said it is "totally ridiculous" to think he's done anything that would amount to an impeachable offense.
In a letter to Comey notifying him of his termination last week, Trump thanks the FBI director for telling him "on three separate occasions" that he is not under investigation.
Rosenstein, the No. 2 Justice Department official, named Mueller amid mounting pressure in Congress for an independent investigation beyond existing FBI and congressional probes into the Russian Federation issue. The memo has not been made available to the public.
Senators said that Rosenstein steered clear of specifics while making clear that Mueller has wide latitude to pursue the investigation wherever it leads, potentially including criminal charges.
But earlier, several lawmakers said Rosenstein told them during a closed Capitol Hill briefing yesterday that Trump made the decision to fire Comey the day before he wrote a memo outlining problems with Comey's handling of the investigation of Hillary Clinton's email server.
Before Comey shook Trump's hand in the White House's Blue Room in footage that has been played often since his ousting, the senior intelligence officer had tried to blend in with the curtains to escape Trump's "inappropriate" behaviour.
The New York Times reported on Thursday that Trump called Comey weeks after he took office on January 20 and asked him when federal authorities were going to say Trump was not under investigation. Trump said he acted because Comey, who had been overseeing the Russian Federation investigation, "wasn't doing a good job" leading the agency, calling him a "showboat" and a "grandstander". It cited two people briefed on the call.
Comey, at the time, advised the president to go send the request to the Justice Department through White House counsel, rather than contacting him directly.
A key issue Mueller may have to tackle is whether Trump has committed obstruction of justice, an offence that could be used in any effort in Congress to impeach him and remove him from office.