WASHINGTON – President Trump on Thursday flatly denied asking ex-FBI Director James Comey to drop his investigation into former national security adviser Michael Flynn, and described Democratic talk of possible impeachment as "totally ridiculous."

Revelations that Comey, whom Trump abruptly fired last week, wrote memos of his past meetings with Trump – including one at which the president apparently asked him to stop an investigation of former national security adviser Michael Flynn – roiled Washington politics this week. On Wednesday, one day after the existence of the memos went public, the Justice Department appointed former FBI Director Robert Mueller as special counsel to oversee the the agency's Russia investigation.

Asked if he did indeed press Comey to stop investigating Flynn, Trump cut off the reporter, saying only: "No, no -- next question."

He also curtly dismissed Washington chatter about the prospect of impeachment for possible obstruction of justice, calling it "totally ridiculous – everybody thinks so."

Trump, in his first live, televised comments about both reports of the Comey memos and Mueller's appointment, said "I respect the move" to appoint a special counsel for the Russia investigation.

Still, he insisted "the entire thing has been a witch hunt" that has divided the country and served as a distraction for his administration's agenda. "We have to get back to running this country really, really well," Trump said at the news conference after meetings with President Juan Manuel Santos of Colombia.

Mueller and his team will oversee the ongoing FBI counterintelligence probe into possible links between Trump campaign associates and Russians who sought to influence the election through hacking and other forms of sabotage to undermine Democrat Hillary Clinton.

Asked about possible collusion with Russia, Trump denies links between his campaign and Moscow – but said, "I can only speak for myself."

Earlier Thursday, Trump took to Twitter on Thursday to denounce the investigation as the "single greatest witch hunt of a politician in American history."

"With all of the illegal acts that took place in the Clinton campaign & Obama Administration, there was never a special counsel appointed!" Trump tweeted.

It was unclear what "illegal acts" Trump was referring to, though as a candidate he did pledge to appoint a special counsel to investigate his Democratic opponent Hillary Clinton's use of private email during her years as secretary of State – a threat he hasn't yet followed up on.

Despite Trump's denunciations on Thursday of the probe, he appeared to accept the decision immediately after it was announced.

"As I have stated many times, a thorough investigation will confirm what we already know – there was no collusion between my campaign and any foreign entity," Trump said in a brief statement Wednesday. "I look forward to this matter concluding quickly. In the meantime, I will never stop fighting for the people and the issues that matter most to the future of our country."

The White House was stunned by the announcement, which they learned about less than an hour before the news became public – and after Deputy Attorney General Rod Rosenstein had already signed the order designating Mueller to lead the Russia probe. Aides agreed to take a low-key approach in the reaction to the news, though some suggested Trump himself dismiss the appointment as unnecessary, which is perhaps what inspired Thursday's tweet reaction.

In the hours after the announcement, the White House said it planned not to answer reporters' questions about the probe and would defer them to the special counsel's office. Though that might be difficult if Trump himself continues to speak out.

The Mueller appointment came little more than a week after Trump fired FBI Director James Comey. While Trump criticized Comey's overall performance, Democrats and some Republicans said it looked like the president was trying to shut down the Russia investigation.

In the news conference Thursday, Trump also said he would appoint a new FBI director soon; he and aides have identified former Connecticut senator Joe Lieberman as a major contender for the slot.

Trump also defended his dismissal of Comey, saying he had done a bad job at the FBI. He said the decision should have had bipartisan support, given Democratic criticism of Comey over his handling of the investigation into presidential candidate Hillary Clinton.