Updated at 5:57 p.m. ET

In his first on-camera remarks amid burgeoning scandals engulfing his White House, President Trump denied he asked then-FBI Director James Comey to scuttle an investigation into his former national security adviser, Michael Flynn.

"No. No. Next question," Trump responded curtly to a reporter during a news conference with Colombian President Juan Manuel Santos on Thursday afternoon.

The press conference was also one of Trump's last opportunities to speak on the record to the American media before his first trip overseas as president later this week.

Comey — whom Trump fired May 9 — wrote a memo memorializing a discussion with the president about Flynn and the FBI's investigation, two sources close to the former FBI director who had seen the memo confirmed to NPR.

And on Tuesday, with that latest report fanning the flames on the growing fallout from Trump's decision to terminate Comey, Deputy Attorney General Rod Rosenstein announced he was appointing former FBI Director Robert Mueller to oversee the Department of Justice investigation into Russian meddling in the 2016 presidential election.

Trump blasted that decision, echoing his Thursday morning tweets and comments he made over lunch with network news anchors that the Russia investigation is a "witch hunt" that "divides the country."

"There is no collusion between, certainly myself and my campaign, but I can only speak for myself and the Russians. Zero," Trump said during the press conference.

"Believe me, there's no collusion," the president continued. "Russia is fine, but whether it's Russia or anybody else, my total priority, believe me, is the United States of America."

"Everybody, even my enemies, have said there was no collusion," Trump added, even though some Democrats have voiced concerns about possible collusion and suggested a thorough investigation was necessary.

Trump also changed his story once again about the circumstances surrounding Comey's firing, returning again to the White House's original rationale that he based his decision on Rosenstein's recommendation. That was the White House's position initially after the deputy attorney general argued in a memo that Comey had erred in handling the FBI's investigation into Democratic nominee Hillary Clinton's private email server, even though Trump had praised Comey on the campaign trail last year.

Trump later said in an interview with NBC News he was going to fire Comey regardless of Rosenstein's recommendation.

Sen. Claire McCaskill, D-Mo., however, told reporters, after Rosenstein briefed the full Senate Thursday afternoon, that the deputy attorney general said he knew Comey would be dismissed by Trump before writing the memo that the White House released when it announced the firing.

Trump also said he would announce his pick to succeed Comey soon and told reporters in the Oval Office with Santos just before their joint news conference that 2000 Democratic vice presidential nominee and former Connecticut Sen. Joe Lieberman was among the finalists.

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