WASHINGTON (CBSNewYork/AP) — President Donald Trump says the decision to appoint former FBI Director Robert Mueller to oversee the investigation into Russian efforts to influence the 2016 presidential election “divides the country.”

“I respect the move, but the entire thing has been a witch hunt,” he said Thursday afternoon, during a joint press conference with Colombian President Juan Manuel Santos. “There was no collusion between certainly myself or my campaign.”

"I respect the move, but the entire thing has been a witch hunt," Pres. Trump says of appointment of special counsel in Russia probe. pic.twitter.com/FWQMmGgfMc — CBS News (@CBSNews) May 18, 2017

“I hate to see anything that divides the country. I’m fine with whatever people want to do, but we have to get back to running this country really, really well,” the president said.

Earlier Thursday, Trump also called the investigation a “witch hunt” on Twitter.

This is the single greatest witch hunt of a politician in American history! — Donald J. Trump (@realDonaldTrump) May 18, 2017

“I don’t think that’s appropriate and I would advise him to stop,” U.S. Sen. Lindsay Graham (R-South Carolina) said. “The process is going to go forward. I’m sure he’s going to try to say it’s a partisan effort, but I don’t think Mueller’s going to be viewed as a partisan guy.”

“I now have significantly greater confidence that the investigation will follow the facts wherever they lead,” Senate Minority Leader Chuck Schumer (D-N.Y.) said.

Meanwhile, Congress will continue to carry out its own investigation and wants former FBI Director James Comey to hand over the memo he wrote, claiming Trump asked him to “back off” the investigation into fired national security adviser Michael Flynn.

“We still would like to hear from Director Comey. The American people need to hear his side of the story,” U.S. Sen. Mark Warner, (D-Virginia) said.

When asked by a reporter whether he advised Comey to back off the investigation, Trump said no.

Speaking about border security, Trump also said “walls work, just ask Israel.”

Asked if he, at any time, urged Comey to close investigation into Flynn, Pres. Trump says: "No. Next question." https://t.co/Okz2bwUl4f pic.twitter.com/8gUT0L0JYI — CBS News (@CBSNews) May 18, 2017

Earlier Thursday, Deputy Attorney General Rod Rosenstein told senators that he knew Comey was going to be fired even before he wrote a memo that provided a basis for Comey’s dismissal.

That’s according to Missouri Democratic Sen. Claire McCaskill. She addressed reporters after a closed-door meeting where Rosenstein briefed senators.

The White House pointed to Rosenstein’s memo last week as justification for Trump’s abrupt decision to dismiss Comey. In the memo Rosenstein criticized Comey’s handling of the Hillary Clinton email investigation.

But Trump himself has already said that he was going to fire Comey regardless and the revelation from McCaskill appeared to bolster that version of events.

“He did acknowledge that he learned Comey would be removed prior to him writing his memo,” McCaskill said.

Following the briefing with Rosenstein, some senators said the Russia probe now appears to be a criminal investigation, CBS2’s Jessica Moore reported.

Trump said Thursday he’s “very close” to naming a new FBI director.

Asked how close he is to making an announcement, Trump answered “soon.”

Trump was also asked whether former Connecticut Sen. Joe Lieberman was among the top contenders for the job. Trump’s response was “He is.”

Trump and Lieberman discussed the position at the White House on Wednesday. Three other potential candidates Trump interviewed on Wednesday are former Oklahoma Gov. Frank Keating, former top FBI official Richard McFeely and Andrew McCabe. McCabe became acting director after Trump fired James Comey as director last week.

Trump has said he could name a new director before he leaves Friday on his first overseas trip as president.

Also Thursday, lawmakers reacted to a Washington Post report of a conversation between House Majority Leader Kevin McCarthy and Paul Ryan, in which McCarthy says Vladimir Putin was paying Trump.

“If you listen to it, you hear everybody laughs. So you know it’s a bad joke,” McCarthy said. “That’s all there is to it. No one believes it to be true.”