"It was a total phony story and I appreciate the special counsel coming out with a statement last night. I think it was very appropriate that they did so," Trump told reporters at the White House on Saturday.
BuzzFeed, citing two unidentified law enforcement officials, reported that Trump directed lawyer Michael Cohen to lie to Congress about a Moscow real estate project and that Cohen told Mueller the president personally instructed him to lie about the timing of the deal.
The report said Mueller's investigators learned about Trump's directive "through interviews with multiple witnesses from the Trump Organization and internal company emails, text messages, and a cache of other documents."
The report said Cohen acknowledged Trump's instructions when he was interviewed by the Mueller team.
The statement by Mueller's office on Friday night doesn't cite any specific errors. Spokesman Peter Carr said that "BuzzFeed's description of specific statements to the special counsel's office, and characterization of documents and testimony obtained by this office, regarding Michael Cohen's congressional testimony are not accurate."
BuzzFeed spokesman Matt Mittenthal said the publication stands by its reporting and urged readers to "stay tuned" as they worked to determine what Mueller was denying. Ben Smith, editor-in-chief of BuzzFeed News, also said the publication stands by its reporting and the sources who informed it.
"We urge the special counsel to make clear what he's disputing," Smith said.
Immediately after the special counsel's statement was issued, Trump retweeted several posts that called the story fake news. He later tweeted: "A very sad day for journalism, but a great day for our Country!"
The extraordinary statement from Mueller's office came after congressional Democrats had pledged to investigate whether the report was true.
The Associated Press had not independently confirmed the report. Any evidence that Trump directed a witness to lie to investigators would place him in the greatest political and legal jeopardy yet.
Cohen pleaded guilty in November to lying to Congress to cover up that he was negotiating the Trump Tower project on Trump's behalf during the heat of his presidential campaign. The charge was brought by Mueller and was the result of Cohen's cooperation with that probe.
Cohen admitted that he lied when he told lawmakers he had never agreed to travel to Russia in connection with the Moscow project and when he said that he'd decided by the end of January 2016 that the "proposal was not feasible for a variety of business reasons and should not be pursued further."
He was sentenced to three years in prison for crimes that included arranging the payment of hush money to conceal his boss' alleged sexual affairs, telling a judge that he agreed time and again to cover up Trump's "dirty deeds" out of "blind loyalty."
Lanny Davis, a Cohen adviser, declined to comment.
Cohen is scheduled to testify publicly before the House Oversight and Reform Committee on Feb. 7. The top Democrat on the Senate Intelligence Committee, Virginia Sen. Mark Warner, said Friday that he expects Cohen to talk to that committee in February.