Robert Mueller's spokesman on Tuesday strongly denied claims in a new Michael Wolff book that the special counsel prepared a draft indictment of President Donald Trump on obstruction of justice.

"The documents described do not exist," Mueller spokesman Peter Carr said, referring to the purported three-count charging document against Trump by the special counsel as reportedly described in Wolff's forthcoming book, "Siege: Trump Under Fire."

It was an unusually blunt and direct response from Carr, who routinely declined to comment during the secretive 20-month investigation.

The supposed draft indictment was detailed Tuesday by The Guardian newspaper, which said it had obtained an advance copy of "Siege" and viewed the documents related to the indictment.

CNBC has not seen either the book, which will be released June 4, or the documents.

Mueller did not charge Trump. The president has repeatedly and adamantly denied any claims of wrongdoing, including suggestions that he interfered with the special counsel's investigation.

Wolff's prior book about Trump, "Fire and Fury," was a runaway best-seller, but also was criticized for containing a number of errors, such as the dates of House Speaker John Boehner's resignation, a claim that Trump did not know who Boehner was in 2016, and misidentifying Commerce Secretary Wilbur Ross' position in the Cabinet.

in "Siege," Wolff says in an author's note that his claims about the indictment are "based on internal documents given to me by sources close to the Office of Special Counsel," according to The Guardian.

The Guardian reported that the document, which Wolff claims sat on Mueller's desk for nearly a year, outlines three charges against the president entitled "United States of America against Donald J Trump, Defendant."

The newspaper says the document accused Trump of corruptly influencing or obstructing a pending investigation; tampering with a witness, victim or information; and retaliating against a witness, victim or information.

According to Wolff's book, as described by The Guardian, the draft outlines the lies told by Trump's first National Security Advisor Michael Flynn to the FBI about his contacts with Russia, the president's effort to have then-FBI Director James Comey "protect Flynn," Comey's subsequent firing and Trump's "attempt to cover up his son [Donald Trump Jr] and son-in-law's [Jared Kushner] meeting with Russian governmental agents."

The bombshell allegation of an indictment prepared — but never executed — against Trump comes three months after Mueller submitted his final report on his investigation of Russian interference in the 2016 presidential election and related issues to Attorney General William Barr.

The report concluded that Russian agents did try to sway the election in Trump's favor by spreading disinformation through social media outlets, and by hacking into computers to obtain emails related to the campaign of Democratic nominee Hillary Clinton. But Mueller did not find that "members of the Trump Campaign conspired or coordinated with the Russian government in its election interference activities."

Mueller did not say one way or the other whether Trump should be charged with obstructing either the special counsel's investigation or a pre-existing inquiry by the Justice Department into Russian meddling and possible collusion by Trump campaign officials.

"Because we determined not to make a traditional prosecutorial judgment, we did not draw ultimate conclusions about the President's conduct," Mueller wrote in his report.

Since 2000, the Justice Department, under whose authority Mueller was operating, has followed guidance of an internal legal advisory memo that says a "sitting President is constitutionally immune from indictment and criminal prosecution."

But Mueller also said his investigation "found multiple acts by the President that were capable of exerting undue influence over law enforcement investigations, including the Russian-interference and obstruction investigations."

And if "we had confidence after a thorough investigation of the facts that the President clearly did not commit obstruction of justice, we would so state," Mueller wrote.

"Based on the facts and the applicable legal standards, we are unable to reach that judgment."